Ultrasonic Measurement Method, Ultrasonic Measurement Apparatus, and Ultrasonic Sensor

ABSTRACT

An ultrasonic measurement method and an ultrasonic measurement apparatus are capable of performing an inspection for a short time with a high SN ratio and a small variation (that depends on an inspection direction) in sensitivity in a process for detecting a defect in all directions at 360 degrees using a matrix array sensor without performing mechanical scanning in all directions, while reducing noise that is caused by a bottom surface echo. An element selecting circuit selects a group of a plurality of ultrasonic transducer elements for transmission from among ultrasonic transducer elements that constitute a two-dimensional array sensor so that the ultrasonic transducer elements for selected for transmission are arranged in line symmetry with respect to a first line symmetric axis to set the group selected for transmission. The element selecting circuit selects a group of a plurality of ultrasonic transducer elements for reception so that the ultrasonic transducer elements selected for reception are arranged in line symmetry with respect to a second line symmetric axis that is perpendicular to the first line symmetric axis to set the group selected for reception. A transmitting element selector selects, as transmitting elements, the ultrasonic transducer elements set by the element selecting circuit. A receiving element selector selects, as receiving elements, the ultrasonic transducer elements set by the element selecting circuit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ultrasonic measurement method and anultrasonic measurement apparatus. The invention more particularlyrelates to an ultrasonic measurement method and an ultrasonicmeasurement apparatus, which are suitable to use phased array transducer(array sensor) having ultrasonic transducer elements that aretwo-dimensionally arranged, and to the ultrasonic sensor.

2. Description of the Related Art

In a conventional technique, when it is difficult to predict a directionin which a defect will become larger, the defect may be overlooked in anultrasonic inspection process for transmitting an ultrasonic wave in anaxial direction and a circumferential direction. Thus, there is demandfor an ultrasonic inspection process for transmitting an ultrasonic wavein all directions. Since this type of defect is detected by an anglebeam inspection process, an ultrasonic inspection technique thatsimultaneously achieves those inspection processes is essential. Inaddition, in order to respond to demand for a reduction in an inspectiontime, it is necessary to develop a technique that is capable ofperforming an ultrasonic inspection process for transmitting anultrasonic wave in all directions without mechanical scanning.

On the other hand, when a fixed-angle sensor is used, mechanical rotaryscanning needs to be performed. In this case, in order to change anincident angle of an ultrasonic wave, the sensor needs to be replaced.Thus, it takes a long time for a measurement. A linear array sensorhaving ultrasonic transducer elements that are one-dimensionallyarranged is capable of performing two-dimension-like scanning by meansof a phased array technique in which the timing for applying an electricsignal to each ultrasonic transducer element is controlled so that anultrasonic beam converges at any refraction angle in a direction inwhich the elements are arranged. Thus, it is not necessary to replacethe sensor. However, in order to perform a measurement in alldirections, mechanical rotary scanning needs to be performed for thesame reason as in the measurement using the fixed-angle sensor.Therefore, it takes a long time for the measurement.

In recent years, a phased array technique that uses a matrix arraysensor having ultrasonic transducer elements two-dimensionally arrangedhas been actively researched and developed in order to reduce themeasurement time (for example, refer to JP-A-2005-351718). In thismethod, it is possible to three-dimensionally transmit and receive anultrasonic wave by controlling the timing for applying an electricsignal in a manner similar to that in the linear array sensor;therefore, it is possible to perform a measurement in all directions fora short time without performing mechanical rotary scanning whileobtaining a good signal-to-noise (SN) ratio.

The present inventors have studied on a three-dimensional ultrasonictechnique that uses a matrix array sensor to inspect a plate materialhaving a large thickness.

It is necessary that a sensor aperture through which an ultrasonic waveis transmitted and received be larger in order to determine whether ornot a crack exists in a deep portion of the plate material in an inspectmethod using the three-dimensional ultrasonic technique.

When the size of a sensor aperture of a matrix array sensor constitutedby ultrasonic transducer elements whose areas are approximately the sameis increased in a manner similar to that in a conventional rectangularmatrix sensor or a segmented sensor array, the number of ultrasonictransducer elements is increased in proportion to the square of the sizeof the sensor aperture.

However, the number of the ultrasonic transducer elements that can becontrolled by a phased array apparatus is restricted for a technicalreason. In addition, even when the number of the ultrasonic transducerelements that can be controlled by the phased array apparatus isincreased, the apparatus would be larger and more expensive; thereforeit is difficult to increase the size of a sensor aperture. In addition,performing a measurement in all directions at 360 degrees using aconventional rectangular matrix array sensor may cause a variation insensitivity due to symmetry of the arrangement of ultrasonic transducerelements constituting the array sensor or due to the shapes of theultrasonic transducer elements.

To avoid the above problems, a method is known which selects, from amongultrasonic transducer elements that are two-dimensionally arranged andconstitute an array sensor, only a group of ultrasonic transducerelements that are arranged in a direction in which electronic scanningis performed and uses the selected elements to transmit and receive anultrasonic wave (for example, refer to JP-5-244691-A).

In addition, another method is known which selects a transmittingelement and a receiving element in a zigzag manner from among ultrasonictransducer elements that constitute an array sensor and aretwo-dimensionally arranged and uses the selected elements to transmitand receive an ultrasonic wave (for example, refer to JP-2003-599-A).

SUMMARY OF THE INVENTION

In the method described in JP-5-244691-A, however, since an ultrasonicwave spreads in a direction perpendicular to a scanning direction in asimilar manner to an ultrasonic wave transmitted by a linear arraysensor, an effect (that is specific to a matrix array sensor and ishereinafter referred to as a point focusing effect) in which theultrasonic wave is three-dimensionally focused on a point cannotdisadvantageously be obtained.

In addition, when an angle at which a defect exists in a measurementangle range (that is close to a normal direction) in which an ultrasonicwave propagates, the ultrasonic wave is reflected from a back surface ofan object to be measured and detected as an echo (bottom surface echo)generated from a bottom surface. In this range, the echo becomes noisefor a corner echo that is caused by a defect that exists on or near theback surface of the object. Even in a range other than theaforementioned range, a high-frequency grating lobe is reflected fromthe bottom surface and becomes noise in a similar manner.

The technique described in JP-2003-599-A alternately selectstransmitting elements and receiving elements from among ultrasonictransducer elements that constitute an array sensor and aretwo-dimensionally arranged in 8 rows and 8 columns so that the selectedtransmitting elements are arranged in every other row and every othercolumn and the selected receiving elements are arranged in every otherrow and every other column, as shown in FIG. 1 of JP-2003-599-A. Thus, adistance between each adjacent pair of the selected transmittingelements and a distance between each adjacent pair of the selectedreceiving elements are twice as large as those in the case in which allthe ultrasonic transducer elements are used as transmitting elements orreceiving elements. When the distance between each adjacent pair of thetransmitting elements and the distance between each adjacent pair of thereceiving elements are large, a grating lobe is generated in a range inwhich a defect is detected. Thus, the defect is superimposed on thegrating lobe. As a result, the defect may not be detected.

An object of the present invention is to provide an ultrasonicmeasurement method and an ultrasonic measurement apparatus, which arecapable of performing a measurement for a short time with a high SNratio and a small variation (that depends on an inspection direction) insensitivity by transmitting and receiving an ultrasonic wave to and froma region (that is to be measured) in a process for detecting a defect inall directions at 360 degrees using a matrix array sensor withoutperforming mechanical scanning in all directions, while maintaining aneffect in which the ultrasonic wave is focused on a point and reducingnoise that is caused by a bottom surface echo.

According to the technique described in JP-5-244691-A, when an arraysensor (having ultrasonic transducer elements arranged in angular rangesthat are the same) or an array sensor (having ultrasonic transducerelements that are not formed in a disk-like shape and having a singleultrasonic transducer element that is arranged at the innermostcircumference of the sensor and is formed in a disk shape) is used, thesizes of ultrasonic transducer elements arranged on an innercircumferential side of the sensor are small depending on the angularrange. Thus, it is difficult to process the sensor during a wiringprocess on the sensor. In addition, sufficient sensitivity cannot beobtained on the inner circumferential side of the sensor, and noise suchas a side lobe may be increased.

According to the measurement method described in JP-A-5-244691 using thesensor that has the shape described in JP-A-5-244691, since theultrasonic transducer elements arranged on the inner circumferentialside are small, directionality of a sound is low and an SN ratio of animage obtained by an inspection cannot be improved.

Another object of the present invention is to provide an ultrasonicmeasurement apparatus that is suitable for inspecting a deep portion ofa plate material having a large thickness with an improved SN ratio andis capable of having a large sensor aperture, and to provide anultrasonic measurement method and an ultrasonic sensor that is used inthe ultrasonic measurement apparatus.

(1) In order to accomplish the aforementioned object, according to thepresent invention, an ultrasonic measurement method using atwo-dimensional array sensor that has a plurality of ultrasonictransducer elements two-dimensionally arranged and using a wavereflected from an inner portion of an object that is to be measured,includes the steps of:

selecting a group of a plurality of ultrasonic transducer elements fortransmission from among the ultrasonic transducer elements thatconstitute the two-dimensional array sensor so that the ultrasonictransducer elements selected for transmission are arranged in linesymmetry with respect to a first line symmetric axis and setting thegroup selected for transmission, and selecting a group of a plurality ofultrasonic transducer elements for reception from among the ultrasonictransducer elements that constitute the two-dimensional array sensor sothat the ultrasonic transducer elements selected for reception arearranged in line symmetry with respect to a second line symmetric axisthat is perpendicular to the first line symmetric axis and passesthrough a rotationally symmetric axis and setting the group selected forreception;

transmitting an ultrasonic wave in the direction of the first linesymmetric axis;

receiving an ultrasonic wave from the direction of the second linesymmetric axis to store a signal reflected from the inner portion of theobject; and

processing the reflected signal to inspect the object.

In the method, it is possible to perform an inspection for a short timewith a high SN ratio and a small variation (that depends on aninspection direction) in sensitivity by transmitting and receiving anultrasonic wave to and from a region (that is to be measured) in aprocess for detecting a defect in all directions at 360 degrees using amatrix array sensor without performing mechanical scanning in alldirections, while maintaining an effect in which the ultrasonic wave isfocused on a point and reducing noise that is caused by a bottom surfaceecho.

(2) Preferably, the ultrasonic measurement method described in the item(1) further may include the steps of:

selecting a group of a plurality of ultrasonic transducer elements fortransmission from among the ultrasonic transducer elements thatconstitute the two-dimensional array sensor so that the ultrasonictransducer elements selected for transmission are arranged in linesymmetry with respect to a third line symmetric axis that is set byrotating the first line symmetric axis by a predetermined angle withrespect to the rotationally symmetric axis, and selecting a group of aplurality of ultrasonic transducer elements for reception from among theultrasonic transducer elements that constitute the two-dimensional arraysensor so that the ultrasonic transducer elements selected for receptionare arranged in line symmetry with respect to a fourth line symmetricaxis that is perpendicular to the third line symmetric axis and passesthrough the rotationally symmetric axis;

transmitting an ultrasonic wave in the direction of the third linesymmetric axis;

receiving an ultrasonic wave from the direction of the fourth linesymmetric axis to store a signal reflected from the inner portion of theobject; and

processing the reflected signal to inspect the object.

(3) In the ultrasonic measurement method described in the item (1), thegroup of the ultrasonic transducer elements selected for transmissionand the group of the ultrasonic transducer elements selected forreception may preferably be arranged so that when the groups are rotatedabout the rotationally symmetric axis by 90 degrees, the groups overlapeach other.

(4) Preferably, the ultrasonic measurement method described in the item(1) further may include the steps of:

setting a plurality of focal points to which ultrasonic waves are to betransmitted by the two-dimensional array sensor;

storing signals reflected from the focal points that are located in theinner portion of the object; and

processing the stored reflected signals to two-dimensionally orthree-dimensionally image the inner portion of the object and display animage of the inner portion of the object.

(5) Preferably, the ultrasonic measurement method described in the item(4) further may include the step of projecting three-dimensionallystored inspection data onto a flat plane and two-dimensionallydisplaying the data on an inspection result display screen.

(6) Preferably, the ultrasonic measurement method described in the item(5) further may include the step of displaying information on arefraction angle φ, an azimuth angle θ and a reflected intensity I.

(7) Preferably, the ultrasonic measurement method described in the item(6) further may include the step of specifying a range of the refractionangle φ to be displayed.

(8) Preferably, the ultrasonic measurement method described in the item(7) further may include the steps of:

performing either an operation for weighting a pulse voltage that is tobe applied to each ultrasonic transducer element selected fortransmission before the transmission of the ultrasonic wave or anoperation for weighting a signal received when the ultrasonic wave isreceived; and

calibrating reflection data and a reflected intensity.

(9) In order to accomplish the aforementioned object, according to thepresent invention, an ultrasonic measurement apparatus includes:

a two-dimensional array sensor having a plurality of ultrasonictransducer elements two-dimensionally arranged;

a transmitting/receiving section that transmits an ultrasonic wave fromeach ultrasonic transducer element included in the two-dimensional arraysensor to an object to be measured and receives a wave reflected fromthe object;

a controller that controls the transmitting/receiving section togenerate three-dimensional or two-dimensional image data; and

a display unit that displays the three-dimensional or two-dimensionalimage data generated by the controller, wherein

the controller includes an element selecting section that selects agroup of a plurality of ultrasonic transducer elements for transmissionfrom among the ultrasonic transducer elements that constitute thetwo-dimensional array sensor so that the ultrasonic transducer elementsselected for transmission are arranged in line symmetry with respect toa first line symmetric axis to set the group selected for transmission,and selects a group of a plurality of ultrasonic transducer elements forreception from among the ultrasonic transducer elements that constitutethe two-dimensional array sensor so that the ultrasonic transducerelements selected for reception are arranged in line symmetry withrespect to a second line symmetric axis that is perpendicular to thefirst line symmetric axis and passes through a rotationally symmetricaxis to set the group selected for reception, and

the transmitting/receiving section includes a transmitting elementselector and a receiving element selector, the transmitting elementselector being adapted to select, as transmitting elements, theultrasonic transducer elements set by the element selecting section, thereceiving element selector being adapted to select, as receivingelements, the ultrasonic transducer elements set by the elementselecting section.

The ultrasonic measurement apparatus is capable of performing aninspection for a short time with a high SN ratio and a small variation(that depends on an inspection direction) in sensitivity by transmittingand receiving an ultrasonic wave to and from a region (that is to bemeasured) in a process for detecting a defect in all directions at 360degrees using a matrix array sensor without performing mechanicalscanning in all directions, while maintaining an effect in which theultrasonic wave is focused on a point and reducing noise that is causedby a bottom surface echo.

(10) In the ultrasonic measurement apparatus described in the item (9),the controller preferably may include either an amplitude adjustingsection or a weighting section, the amplitude adjusting section beingadapted to weight a pulse voltage that is to be applied to eachultrasonic transducer element selected for transmission before thetransmission of the ultrasonic wave, the weighting section being adaptedto weight a signal received when the ultrasonic wave is received.

(2-1) In order to accomplish the aforementioned object, according to thepresent invention, an ultrasonic measurement apparatus includes:

a two-dimensional array sensor having a plurality of ultrasonictransducer elements two-dimensionally arranged;

a transmitting/receiving section that transmits an ultrasonic wave fromthe two-dimensional array sensor and receives a wave reflected from aninner portion of an object that is to be measured; and

a controller that controls the transmitting/receiving section to causethe transmitting/receiving section to transmit the ultrasonic wave andreceive the ultrasonic wave;

wherein the two-dimensional array sensor has an inner circumferentialportion and an outer circumferential portion, the arrangement of theultrasonic transducer elements included in the inner circumferentialportion being different from the arrangement of the ultrasonictransducer elements included in the outer circumferential portion,

a distance between the gravity centers of each adjacent pair of theultrasonic transducer elements included in the inner circumferentialportion is equal to or less than a distance at which noise such as agrating lobe is not caused,

a distance between the gravity centers of each adjacent pair of some ofthe ultrasonic transducer elements included in the outer circumferentialportion is equal to or less than the distance at which noise such as agrating lobe is not caused, and a distance between the gravity centersof each adjacent pair of the other ultrasonic transducer elementsincluded in the outer circumferential portion is larger than thedistance at which such as a grating lobe is not caused,

the controller has an element selecting circuit that selects an elementthat is to be used from among the plurality of ultrasonic transducerelements that constitute the two-dimensional array sensor,

the element selecting circuit selects all the ultrasonic transducerelements included in the inner circumferential portion and ultrasonictransducer elements included in the outer circumferential portion sothat a distance between the gravity centers of each adjacent pair of theselected transducer elements included in the outer circumferentialportion, wherein the distance is measured in a transmitting andreceiving direction obtained by projecting a direction in which anultrasonic is transmitted and received onto a surface of the arraysensor, is equal to or less than the distance at which noise is notcaused.

The ultrasonic measurement apparatus described in the item (11) issuitable for inspecting a deep portion of a plate material having alarge thickness with an improved SN ratio and is capable of having alarge sensor aperture.

(2-2) In the ultrasonic measurement apparatus described in the item(2-1), the element selecting circuit may preferably select elementswhose gravity centers are located in a rectangular region having a longside that extends in the projected transmitting and receiving directionand a short side whose length is equal to the diameter of the innercircumferential portion.

(2-3) To accomplish the aforementioned object, according to the presentinvention, an ultrasonic sensor that transmits an ultrasonic wave andhas a plurality of two-dimensionally ultrasonic transducer elementsarranged, the ultrasonic sensor being used in an ultrasonic measurementapparatus that performs an inspection using a wave reflected from aninner portion of an object that is to be measured, includes:

an inner circumferential portion and an outer circumferential portion inwhich the arrangement of the ultrasonic transducer elements included inthe inner circumferential portion is different from the arrangement ofthe ultrasonic transducer elements included in the outer circumferentialportion,

wherein a distance between the gravity centers of each adjacent pair ofthe ultrasonic transducer elements included in the inner circumferentialportion is equal to or less than a distance at which such as a gratinglobe is not caused, and

a distance between the gravity centers of each adjacent pair of some ofthe ultrasonic transducer elements included in the outer circumferentialportion is equal to or less than the distance at which noise such as agrating lobe is not caused, and a distance between the gravity centersof each adjacent pair of the other ultrasonic transducer elementsincluded in the outer circumferential portion is larger than thedistance at which noise such as a grating lobe is not caused.

The ultrasonic sensor is suitable for inspecting a deep portion of aplate material having a large thickness with an improved SN ratio and iscapable of having a large sensor aperture.

(2-4) To accomplish the aforementioned object, according to the presentinvention, an ultrasonic measurement method using a two-dimensionalarray sensor that has a plurality of ultrasonic transducer elementstwo-dimensionally arranged to transmit an ultrasonic wave and using awave reflected from an inner portion of an object that is to bemeasured, includes the steps of:

using the two-dimensional array sensor that has an inner circumferentialportion and an outer circumferential portion, the arrangement of theultrasonic transducer elements included in the inner circumferentialportion being different from the arrangement of the ultrasonictransducer elements included in the outer circumferential portion,wherein a distance between the gravity centers of each adjacent pair ofthe ultrasonic transducer elements included in the inner circumferentialportion is equal to or less than a distance at which noise such as agrating lobe is not caused, a distance between the gravity centers ofeach adjacent pair of some of the ultrasonic transducer elementsincluded in the outer circumferential portion is equal to or less thanthe distance at which noise is caused, and a distance between thegravity centers of each adjacent pair of the other the ultrasonictransducer elements included in the outer circumferential portion islarger than the distance at which noise is not caused; and

selecting all the ultrasonic transducer elements included in the innercircumferential portion and ultrasonic transducer elements that areadjacent to each other and included in the outer circumferential portionand whose gravity centers are separated with a distance that is equal toor less than the distance at which noise is not caused for theinspection of the object, the distance between the gravity centers ofeach adjacent pair of the selected elements included in the outercircumferential portion being measured in a direction obtained byprojecting, onto the surface of the array sensor, a direction in whichthe ultrasonic wave is transmitted and received.

The ultrasonic measurement method described in the item (2-4) issuitable for inspecting a deep portion of a plate material having alarge thickness with an improved SN ratio and is capable of having alarge sensor aperture.

(2-5) Preferably, the ultrasonic measurement method described in theitem (2-4) further may include the steps of:

setting a plurality of focal points to which ultrasonic waves are to betransmitted by the two-dimensional array sensor;

selecting a range of elements to be used for transmission and receptionof the ultrasonic waves to the focal points;

storing signals reflected from the focal points located in the innerportion of the object; and

processing the stored reflected signals to two-dimensionally orthree-dimensionally image the inner portion of the object.

According to the invention, it is possible to perform an inspection fora short time with a high SN ratio and a small variation (that depends onan inspection direction) in sensitivity by transmitting and receiving anultrasonic wave to and from a region (that is to be measured) in aprocess for detecting a defect in all directions at 360 degrees using amatrix array sensor without performing mechanical scanning in alldirections, while maintaining an effect in which the ultrasonic wave isfocused on a point and reducing noise that is caused by a bottom surfaceecho.

According to another invention, the ultrasonic measurement apparatus issuitable for inspecting a deep portion of a plate material having alarge thickness with an improved SN ratio and is capable of having alarge sensor aperture.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the entire configuration of anultrasonic measurement apparatus according to a first embodiment of thepresent invention.

FIG. 2 is a diagram showing the configuration of a two-dimensional arraysensor that is used in the ultrasonic measurement apparatus according tothe first embodiment of the present invention.

FIG. 3 is a flowchart of a method for selecting a transmitting elementand a receiving element from among elements that are included in theultrasonic measurement apparatus according to the first embodiment ofthe present invention.

FIG. 4 is a diagram showing a table that indicates combinations ofultrasonic transducer elements that are to be used for transmission andreception and are included in the ultrasonic measurement apparatusaccording to the first embodiment of the present invention.

FIG. 5 is a flowchart of another method for selecting a transmittingelement and a receiving element from among the elements that areincluded in the ultrasonic measurement apparatus according to the firstembodiment of the present invention.

FIG. 6 is a diagram showing another table that indicates combinations ofultrasonic transducer elements that are to be used for transmission andreception and are included in the ultrasonic measurement apparatusaccording to the first embodiment of the present invention.

FIG. 7 is a diagram showing another table that indicates combinations ofultrasonic transducer elements that are to be used for transmission andreception and are included in the ultrasonic measurement apparatusaccording to the first embodiment of the present invention.

FIGS. 8A and 8B are diagrams each showing an imaging operation that isperformed by the ultrasonic measurement apparatus according to the firstembodiment of the present invention.

FIG. 9 is a diagram showing a region that is measured by the ultrasonicmeasurement apparatus according to the first embodiment of the presentinvention.

FIGS. 10A and 10B diagrams each showing an example of an image displayedby the ultrasonic measurement apparatus according to the firstembodiment of the present invention.

FIG. 11 is a flowchart showing content of a displaying process that isperformed by the ultrasonic measurement apparatus according to the firstembodiment of the present invention.

FIG. 12 is a flowchart showing other content of the displaying processthat is performed by the ultrasonic measurement apparatus according tothe first embodiment of the present invention.

FIG. 13 is a diagram showing a first example of a combination ofultrasonic wave transmitting elements included in the ultrasonicmeasurement apparatus according to the first embodiment of the presentinvention and a combination of ultrasonic wave receiving elementsincluded in the ultrasonic measurement apparatus according to the firstembodiment of the present invention.

FIG. 14 is a diagram showing a second example of a combination ofultrasonic wave transmitting elements included in the ultrasonicmeasurement apparatus according to the first embodiment of the presentinvention and a combination of ultrasonic wave receiving elementsincluded in the ultrasonic measurement apparatus according to the firstembodiment of the present invention.

FIG. 15 is a diagram showing a third example of a combination ofultrasonic wave transmitting elements included in the ultrasonicmeasurement apparatus according to the first embodiment of the presentinvention and a combination of ultrasonic wave receiving elementsincluded in the ultrasonic measurement apparatus according to the firstembodiment of the present invention.

FIG. 16 is a diagram showing a fourth example of a combination ofultrasonic wave transmitting elements included in the ultrasonicmeasurement apparatus according to the first embodiment of the presentinvention and a combination of ultrasonic wave receiving elementsincluded in the ultrasonic measurement apparatus according to the firstembodiment of the present invention.

FIG. 17 is a diagram showing a fifth example of a combination ofultrasonic wave transmitting elements included in the ultrasonicmeasurement apparatus according to the first embodiment of the presentinvention and a combination of ultrasonic wave receiving elementsincluded in the ultrasonic measurement apparatus according to the firstembodiment of the present invention.

FIG. 18 is a block diagram showing the entire configuration of anultrasonic measurement apparatus according to a second embodiment of thepresent invention.

FIG. 19 is a flowchart showing content of a method for determining aweighting constant for the ultrasonic measurement apparatus according tothe second embodiment of the present invention.

FIG. 20 a flowchart showing content of a method for determining aweighting constant for the ultrasonic measurement apparatus according tothe second embodiment of the present invention.

FIG. 21 is a flowchart of a method for selecting a transmitting elementand a receiving element from among ultrasonic transducer elementsincluded in an ultrasonic measurement apparatus according to a thirdembodiment of the present invention.

FIG. 22 is a diagram showing the selected transmitting and receivingelements that are included in the ultrasonic measurement apparatusaccording to the third embodiment of the present invention.

FIG. 23 is a diagram showing selected transmitting elements and selectedreceiving elements that are included in an ultrasonic measurementapparatus according to a fourth embodiment of the present invention.

FIG. 24 is a block diagram showing the configuration of an ultrasonicmeasurement apparatus according to a fifth embodiment of the presentinvention.

FIG. 25 is a plan view showing the configuration of an array sensor thatis used in the ultrasonic measurement apparatus according to the fifthembodiment of the present invention.

FIG. 26 is a schematic diagram showing the positions of the gravitycenters of elements included in the array sensor that is used in theultrasonic measurement apparatus according to the fifth embodiment ofthe present invention.

FIG. 27 is a diagram showing an inspection method that is performed bythe ultrasonic measurement apparatus according to the fifth embodimentof the present invention.

FIG. 28 is a diagram showing the array sensor that is used in theultrasonic measurement apparatus according to the fifth embodiment ofthe present invention.

FIG. 29 is a diagram showing a method for selecting an element that isincluded in the sensor that is used in the ultrasonic measurementapparatus according to the fifth embodiment of the present invention.

FIG. 30 is a flowchart showing content of the inspection method that isperformed by the ultrasonic measurement apparatus according to the fifthembodiment of the present invention.

FIG. 31 is a diagram showing a pattern of elements that are to be usedand are included in the ultrasonic measurement apparatus according tothe fifth embodiment of the present invention.

FIG. 32 is a diagram showing a pattern of elements that are to be usedand are included in the ultrasonic measurement apparatus according tothe fifth embodiment of the present invention.

FIG. 33 is a plan view of another configuration of the array sensor thatis used in the ultrasonic measurement apparatus according to the fifthembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The configuration and operations of an ultrasonic measurement apparatusaccording to a first embodiment of the present invention are describedwith reference to FIGS. 1 to 17.

First, the entire configuration of the ultrasonic measurement apparatusaccording to the present embodiment is described with reference to FIG.1.

FIG. 1 is a block diagram showing the entire configuration of theultrasonic measurement apparatus according to the present embodiment.

The ultrasonic measurement apparatus according to the present embodimentmeasures an object 100 and a reflection source 100A located inside theobject or located on the surface of the object with an excellent SNratio. The ultrasonic measurement apparatus according to the presentembodiment has a probe 101, a transmitting/receiving section 102, acontroller 103, and a display unit 104.

The probe 101 includes an array sensor 101B that transmits and receivesan ultrasonic wave to the object 100 that is to be measured. The arraysensor 101B has a plurality of ultrasonic transducer elements 101A.

The transmitting/receiving section 102 has a pulsar 102A and a receiver102Z. The pulsar 102A provides a delay time to the array sensor 101B sothat the array sensor 101B transmits an ultrasonic wave on the basis ofthe delay time. The receiver 102Z receives an ultrasonic wave, andconverts the received analog ultrasonic wave into a digital signal as areception signal.

The controller 103 has a control processing computer 103A, an elementselecting circuit 103C, a delay time control circuit 103D, and an addingcircuit 103Z. The control processing computer 103A has a storage device103B. The element selecting circuit 103C controls the ultrasonictransducer elements 101A when necessary. Specifically, the elementselecting circuit 103C switches between ultrasonic transducer elements101A that are to be used for transmission of an ultrasonic wave andswitches between ultrasonic transducer elements 101A that are to be usedfor reception of an ultrasonic wave. The delay time control circuit 103Dcontrols the delay time that is used for transmission of an ultrasonicwave and a delay time that is used for reception of an ultrasonic wave.The adding circuit 103Z receives a plurality of signals from thereceiver 102Z and adds the received signals. The control processingcomputer 103A controls the element selecting circuit 1030, the delaytime control circuit 103D and the adding circuit 103Z and stores areceived signal in the storage device 103B. The control processingcomputer 103A performs processing on the received signal.

The display unit 104 has a setting input screen 104A and a displayscreen 104Z. Various settings can be displayed on the setting inputscreen 104A and can be input using the setting input screen 104A. Asignal received by the display unit 104 and an image obtained by ameasurement are displayed on the display screen 104Z.

Next, operations of the sections of the apparatus are described below.

The control processing computer 103A transmits a transmitting/receivingelement switching signal that is used to select an ultrasonic transducerelement to be used to transmit/receive an ultrasonic wave to the elementselecting circuit 103C upon storing a reflection signal received fromthe object that is to be measured by transmission and reception of theultrasonic wave. In addition, the control processing computer 103Aprovides, through the delay control circuit 103D, a delay time to eachultrasonic transducer element so that the element transmits anultrasonic wave that will be focused and receives an ultrasonic wave.

A transmission delay circuit 102B receives the transmitted signal andthe delay time and transmits the signal (transmission signal) to atransmitting element selector 102C after a time specified by thereceived delay time.

The transmitting element selector 102C receives the transmission signalhaving the delay time added thereto from the transmission delay circuit102B. The transmitting element selector 102C then selects a transmittingelement on the basis of a selection signal (that is used to select thetransmitting element) transmitted from the element selecting circuit103C and transmits the transmission signal to a transmission amplifier102E. The transmitting element selector 102C selects a receiving elementon the basis of a receiving element switching signal transmitted fromthe control processing computer 103A. The present embodiment ischaracterized in a method for selecting a transmitting element and areceiving element by means of the transmitting element selector 102C,and the method is described in detail with reference to FIGS. 13 to 17.

The transmission amplifier 102E amplifies the transmission signal andapplies, to the ultrasonic transducer elements 101A included in thearray sensor 101B, a drive voltage that is used to transmit anultrasonic wave. In this case, the transmitting element selector 102C iscapable of separately transmitting signals to an N number of ultrasonictransducer elements 101A included in the array sensor 101B orsimultaneously transmitting signals to a plurality of ultrasonictransducer elements 101A included in the array sensor 101B.

The plurality of ultrasonic transducer elements 101A receives theamplified signals and transmits ultrasonic waves by means of apiezoelectric effect. The present embodiment describes transmission andreception of ultrasonic waves by the ultrasonic transducer elements 101Aincluded in the array sensor 101B.

As described above, when the delay time is added to the transmissionsignal and a voltage is applied to each ultrasonic transducer element101A on the basis of the delay time, the ultrasonic transducer element101A transmits an ultrasonic wave after the time specified by the delaytime. In order to focus the ultrasonic waves on a certain point, avoltage is applied to each ultrasonic transducer element after a timespecified by the delay time corresponding to a geometric distancebetween the ultrasonic transducer element and the focal point, i.e., thedistance determined in consideration of the velocity of the ultrasonicwave in each medium and refraction at the boundary between the media. Inthis way, the ultrasonic waves are transmitted and focused (for example,when a defect 100A exists in the object 100 that is to be measured, theultrasonic waves are focused on a focal point 100B so that the defectcan be detected with a high SN ratio) on a predetermined portion of theobject 100.

The receiver 102Z receives ultrasonic waves and processes electricsignals generated by means of a piezoelectric effect. In order toprocess the electric signals, an amplifier 102Y receives signals(reception signals) corresponding to the ultrasonic waves received bythe ultrasonic transducer elements 101A and amplifies the receptionsignals, and an analog-digital converter 102X converts the analogreceived signals into digital signals.

A receiving element selector 102W receives a signal from the receivingelement selected by means of a command transmitted from the transmittingelement selector 102C. The reception signal is converted into a digitalsignal, and selected and stored in a delay memory 102V. When theultrasonic waves are focused on the focal point 100B in a similar mannerto ultrasonic wave transmission and reception, the delay timetransmitted from the delay control circuit 103D is added to thereception signal transmitted from each ultrasonic transducer element,and the signal having the delay time added thereto is stored in thedelay memory 102V.

The adding circuit 103Z included in the controller 103 adds thereception signals and transmits the thus-obtained signal to the controlprocessing computer 103A.

Next, a method for selecting a transmitting element and a receivingelement, which are included in the ultrasonic measurement apparatusaccording to the present embodiment, is described below with referenceto FIGS. 2 to 4.

FIG. 2 is a diagram showing the configuration of the two-dimensionalarray sensor that is used in the ultrasonic measurement apparatusaccording to the first embodiment of the present invention. FIG. 3 is aflowchart of a method for selecting a transmitting element and areceiving element, which are included in the ultrasonic measurementapparatus according to the first embodiment of the present invention.FIG. 4 is a diagram showing a table that indicates combinations ofultrasonic transducer elements that are to be used for transmission andreception and are included in the ultrasonic measurement apparatusaccording to the first embodiment of the present invention.

The following describes procedures for selecting an ultrasonictransducer element that is to be used to transmit/receive an ultrasonicwave so as to improve an SN ratio. The ultrasonic transducer elementsare selected from among the elements included in the apparatus describedwith reference to FIG. 1.

In order to perform setting on the setting input screen 104A, thefollowing information is necessary: the sizes, positions and arrangementof the ultrasonic transducer elements that constitute the array sensor.

FIG. 2 schematically shows the array sensor 101B having the ultrasonictransducer elements that are two-dimensionally arranged.

It is assumed that the array sensor 101B has an N number of ultrasonictransducer elements 101A arranged in P rows and Q columns (P×Q=N). Inorder to set the velocity of an ultrasonic wave to be transmitted to theobject and to set the arrangement of the N number of ultrasonictransducer elements 101A that constitute the array sensor 101B and aretwo-dimensionally arranged and pitches between the ultrasonic transducerelements 101A, a pitch Lx between each adjacent pair of the ultrasonictransducer elements 101A arranged in a vertical direction and a pitch Lybetween each adjacent pair of the ultrasonic transducer elements 101Aarranged in a horizontal direction are set (shown in FIG. 2). Thus, thepositions of the ultrasonic transducer elements 101A that are arrangedin the array sensor 101B can be recognized.

Next, the procedures for the setting are described with reference toFIG. 3.

When the setting is started, an inspector uses the setting input screen104A (shown in FIG. 1) to enter, as initial settings for the arraysensor, necessary information such as information on the ultrasonictransducer elements that constitute the array sensor and the velocity ofan ultrasonic wave in step S101.

Then, the position of the center of the sensor having the N number ofultrasonic transducer elements, which is a reference of the delay timeand image display, is set in step S102. In general, the center(intersection of a central line Cy and a central line Cx) of theultrasonic transducer elements is set as the center C of the sensor.

Next, the control processing computer 103A calculates a pattern of delaytimes for the respective ultrasonic transducer elements that areincluded in the array sensor in step S103.

Meanwhile, the element selecting circuit 103C uses the informationprovided in the initial setting of step S101 to set an ultrasonictransducer element group that is to be used for transmission andreception in step S104.

The transmitting/receiving section 102 transmits and receives anultrasonic wave on the basis of these settings in step S105, and data isstored in step S106. Then, the process is ended.

In order to simply set a combination of ultrasonic transducer elementsto be used for transmission and a combination of ultrasonic transducerelements to be used for reception, the following operations may beperformed: data on combinations of ultrasonic transducer elements to beused for transmission and reception is pre-stored in the storage device103B (shown in FIG. 1) included in the control processing computer 103A;a combination pattern of ultrasonic transducer elements to be used fortransmission and reception is specified; the specified pattern is readwhen an inspection starts; the transmitting element selector 102C isoperated in order to perform the transmission; and the receiving elementselector 102W is operated in order to perform the reception.

FIG. 4 shows an example of the table that indicates combinations ofultrasonic transducer elements that are to be used for transmission andreception.

As shown in FIG. 4, combinations of ultrasonic transducer elements to beused for transmission and reception are arranged in a vertical directionof FIG. 4. Element numbers (for example, element numbers of the elementsshown in FIG. 2) of the ultrasonic transducer elements constituting thearray sensor are displayed. In addition, ON and OFF states oftransmitting elements (P) 401 and receiving elements (R) 402 aredisplayed and indicated by 1 and 0, respectively. The transmittingelements (P) 401 and the receiving elements (R) 402 are the ultrasonictransducer elements.

The following describes another method for selecting a transmittingelement and a receiving element, which are included in the ultrasonicmeasurement apparatus according to the present embodiment with referenceto FIGS. 5 to 7.

FIG. 5 is a flowchart of the method for selecting a transmitting elementand a receiving element, which are included in the ultrasonicmeasurement apparatus according to the present embodiment. FIG. 6 is adiagram showing another table that indicates combinations of ultrasonictransducer elements that are to be used for transmission and receptionand are included in the ultrasonic measurement apparatus according tothe embodiment of the present invention. FIG. 7 is a diagram showinganother table that indicates combinations of ultrasonic transducerelements that are to be used for transmission and reception and areincluded in the ultrasonic measurement apparatus according to theembodiment of the present invention.

FIG. 5 is a flowchart of the selection method that is performed on aplurality of focal points F (i).

When the setting is started, the inspector uses the setting input screen104A (shown in FIG. 1) to enter, as initial settings for the arraysensor, necessary information such as information on the ultrasonictransducer elements that constitute the array sensor and the velocity ofan ultrasonic wave in step S101.

Then, the position of the center of the sensor having the N number ofultrasonic transducer elements, which is a reference of the delay timeand image display, is set in step S102. In general, the center(intersection of the central line Cy and the central line Cx) of theultrasonic transducer elements is set as the center C of the sensor.

Next, the control processing computer 103A calculates a focal point F(on which an ultrasonic wave transmitted by each ultrasonic transducerelement included in the array sensor is focused) and a delay time (fortransmission by each ultrasonic transducer element included in the arraysensor) and sets the focal point F and the delay time in step S107.

Meanwhile, the element selecting circuit 103C uses the informationprovided in the initial setting of step S101 to set an ultrasonictransducer element group to be used for transmission and an ultrasonictransducer element group to be used for reception in step S104.

The transmitting/receiving section 102 transmits and receives ultrasonicwaves as set in the aforementioned manner to and from each focal point F(i) in step S105A, and data (reflection data) obtained from the focalpoint F (i) is stored in step S106A.

It is determined whether or not data on all directions is completelystored in step S108. When the operation for storing the data on all thedirections is not ended (or when the answer in step S108 is NO), theprocess returns to step S105A and an ultrasonic wave is transmitted tothe next focal point F (i+1) and received from the focal point F (i+1).The operation for storing reflection data is sequentially repeated untilreflection data on all regions to be measured is completely stored.

When the operation for storing the data on all the directions is ended(or when the answer in step S108 is YES), the control processingcomputer 103A creates a map indicative of pixels and pixel values instep S109 and causes an image to be displayed in step S110. Then, theprocess is ended.

In order to simply set a combination of ultrasonic transducer elementsto be used for transmission and a combination of ultrasonic transducerelements to be used for reception, the following operations may beperformed: the table (shown in FIG. 4) indicative of combinations ofultrasonic transducer elements to be used for transmission andcombinations of ultrasonic transducer elements to be used for receptionis pre-stored in the storage device 103B (shown in FIG. 1); acombination of ultrasonic transducer elements to be used fortransmission and a combination of ultrasonic transducer elements to beused for reception are read when a measurement starts; the transmittingelement selector 102C is operated in order to perform the transmission;and the receiving element selector 102W is operated in order to performthe reception.

FIG. 6 shows an example of a table that indicates a delay time that isto be given to each ultrasonic transducer element to be used fortransmission and to each ultrasonic transducer element to be used forreception. Methods for setting a delay time are described in variousdocuments. For example, a method for setting a delay time is describedin a medical ultrasonic apparatus handbook.

A combination of ultrasonic transducer elements to be used to transmitultrasonic waves to the focal points F (i) and a combination ofultrasonic transducer elements to be used to receive ultrasonic wavesfrom the focal points F (i) are selected. The selected combinations arereflected in the transmitting element selector 102C and the receivingelement selector 102W, respectively so that the ultrasonic transducerelements to be used for transmission and reception are restricted.

FIG. 7 shows an example of a table formed by combining the delay timetable shown in FIG. 4 and the table (shown in FIG. 6) indicative of thecombinations of ultrasonic transducer elements. In FIG. 7, an ON stateis indicated by a positive delay time (Pik, Rik), and an OFF state isindicated by −1.

Next, an imaging operation by the ultrasonic measurement apparatusaccording to the present embodiment is described with reference to FIGS.8A to 11.

FIGS. 8A and 8B are diagrams showing the imaging operation that isperformed by the ultrasonic measurement apparatus according to the firstembodiment of the present invention. FIG. 9 is a diagram showing aregion to be measured by the ultrasonic measurement apparatus accordingto the first embodiment of the present invention. FIGS. 10A and 10B arediagrams each showing an example of an image displayed by the ultrasonicmeasurement apparatus according to the first embodiment of the presentinvention. FIG. 11 is a flowchart showing content of a displayingprocess that is performed by the ultrasonic measurement apparatusaccording to the first embodiment of the present invention. FIG. 12 is aflowchart showing other content of the displaying process that isperformed by the ultrasonic measurement apparatus according to the firstembodiment of the present invention.

The schematic diagram of FIG. 8A shows the state in which data D (F (i))on the focal points F (i) set on the basis of the delay times areobtained by electronic scanning and stored. In the data D (F (i)), theabscissa represents a path length (R), and the ordinate represents theintensity (I), as shown on the upper left side of FIG. 8A.

Various signal processing such as detection processing, gain processing,and filter processing are performed on the data D (F (i)). After that,the data is converted into image data, or the data on each focal pointis converted into image data. Then, interpolation processing isperformed on the data so that a three-dimensional image is displayed. Asa result, three-dimensional measurement results are obtained from ameasured region MA shown in FIG. 9.

A three-dimensional imaging operation is performed in athree-dimensional measurement process using an ultrasonic wave and themeasurement results are displayed in general. However, it takes time toperform data processing and display data. To avoid this, a method fordowngrading the display method from the 3D display method to a 2Ddisplay method in the ultrasonic inspection process is described withreference to FIGS. 8A and 8B.

The sensor 101B shown in FIG. 8A transmits and receives ultrasonic wavesto and from the focal points F (i) to obtain the data D (F (i)). Thedata D (F (i)) is regarded as data having an azimuth angle (φ), arefraction angle (θ), and a path length as variables for each intensity(I). The data is converted and projected onto a projective plane PLshown in FIG. 8B using the following formula.

I(R, θ, φ)->I(R sin θ cos φ, R sin θ sin φ)  (1)

The azimuth angle (φ), the refraction angle (θ) and the depth (Z) areshown in FIG. 9.

In FIG. 8B, the surface 101B′ of the sensor is projected onto theprojective plane PL. The data D (F (i)) projected on the projectiveplane PL is subjected to interpolation processing in association withthe intensities (I) of the data D (F (i)) projected on pixels Aij of theprojective plane PL in a similar manner to an operation for displaying asector image. As shown in FIG. 10A, the thus obtained data is displayedon the display screen 104Z shown in FIG. 1. In an example of FIG. 10A, adefect echo Ed and a bottom surface echo Eb are shown.

However, the data D (F (i)) projected on the projective plane PL mayoverlap depending on the method for setting the focal points, as shownin FIG. 8B. In this case, adding and average processing may be performedon each focal point.

As an ideal method, the focal points are set in a refraction angle rangein which the measurement needs to be performed under the condition thatthe data is prevented from overlapping each other.

When the data is displayed, there is a range in which a desired signalis not returned depending on the bottom surface echo or an insensitiveregion. Thus, the focal points may be set outside the aforementionedrange. Alternatively, the focal points may be stored, and only focalpoints within a specified refraction angle range may be displayed asshown in FIG. 10B. Specifically, the minimum angle θ1 for display isset, and a region that is smaller than a region defined by the minimumangle θ1 is not displayed. It should be noted that an angle θ2 is themaximum angle for display.

Next, procedures for displaying the measurement results described withreference to FIGS. 8A to 10B are described with reference to FIG. 11.

When the data processing is performed on the stored data, the controlprocessing computer 103A receives data on one waveform from among allthe stored data in step S201.

Next, coordinate conversion is performed on the one-waveform data instep S202. Then, it is determined whether or not the coordinateconversion of all the data is ended in step S203. When the coordinateconversion of all the data is not ended (or when the answer in step S203is NO), the control processing computer 103A receives the data on thenext waveform and performs data processing on the data on the nextwaveform.

When the coordinate conversion of all the data is ended (or when theanswer in step S203 is YES), data mapping is performed in step S204.Then, a display range (refraction angle range) is specified in stepS205, and an image is displayed in step S206. Then, the process isended.

Next, other procedures for displaying the measurement results describedwith reference to FIGS. 8A to 10B are described with reference to FIG.12.

When the shape of a target to be measured is known, a range of the pathlength of data is pre-specified so that an unwanted signal is notdisplayed, as described below.

When the data processing is performed on the stored data, the controlprocessing computer 103A receives the stored data on one waveform instep S201′ (S201B).

A path length range that needs to be extracted from the data on the onewaveform is input in step S207.

The data on the one waveform, which corresponds to an input depth range,is extracted in step S208.

Next, coordinate conversion is performed on the one-waveform data instep S202. Then, it is determined whether or not coordinate conversionof all the data is ended in step S203. When the coordinate conversion ofall the data is not ended (or when the answer in step S203 is NO), thecontrol processing computer 103A receives the data on the next waveformand performs data processing on the data on the next waveform.

When the coordinate conversion of all the data is ended (or when theanswer in step S203 is YES), data mapping is performed in step S204. Theimage is reconfigured in step S209. Then, a display range (refractionangle range) is specified in step S205, and the image is displayed instep S206. Then, the process is ended.

The ultrasonic measurement apparatus may have a function of displayinginformation on the refraction angle (θ), the azimuth angle (φ), and theintensity (I) when a cursor is placed on the image shown in FIG. 10A or10B.

In order to obtain high resolution (for visualization) for a certainaddress of a signal, the image may be colored on the basis of theintensities (I) shown in the data D (F (i)).

Next, combinations of ultrasonic wave transmitting elements included inthe ultrasonic measurement apparatus according to the present embodimentand combinations of ultrasonic wave receiving elements included in theultrasonic measurement apparatus according to the present embodiment aredescribed with reference to FIGS. 13 to 17.

FIG. 13 is a diagram showing a first example of a combination ofultrasonic wave transmitting elements included in the ultrasonicmeasurement apparatus according to the first embodiment of the presentinvention and a combination of ultrasonic wave receiving elementsincluded in the ultrasonic measurement apparatus according to the firstembodiment of the present invention. FIG. 14 is a diagram showing asecond example of a combination of ultrasonic wave transmitting elementsincluded in the ultrasonic measurement apparatus according to the firstembodiment of the present invention and a combination of ultrasonic wavereceiving elements included in the ultrasonic measurement apparatusaccording to the first embodiment of the present invention. FIG. 15 is adiagram showing a third example of a combination of ultrasonic wavetransmitting elements included in the ultrasonic measurement apparatusaccording to the first embodiment of the present invention and acombination of ultrasonic wave receiving elements included in theultrasonic measurement apparatus according to the first embodiment ofthe present invention. FIG. 16 is a diagram showing a fourth example ofa combination of ultrasonic wave transmitting elements included in theultrasonic measurement apparatus according to the first embodiment ofthe present invention and a combination of ultrasonic wave receivingelements included in the ultrasonic measurement apparatus according tothe first embodiment of the present invention. FIG. 17 is a diagramshowing a fifth example of a combination of ultrasonic wave transmittingelements included in the ultrasonic measurement apparatus according tothe first embodiment of the present invention and a combination ofultrasonic wave receiving elements included in the ultrasonicmeasurement apparatus according to the first embodiment of the presentinvention.

As described above, in the method and apparatus using the array sensoraccording to the present embodiment, a single reflection signal and aplurality of reflection signals are stored by means of a combination ofultrasonic wave transmitting elements and a combination of ultrasonicwave receiving elements. Thus, various combinations of ultrasonic wavetransmitting elements and various combinations of ultrasonic wavereceiving elements can be used. In addition, an ultrasonic wave can betransmitted in various directions and can be received from variousdirections.

First, the first example of the combination of the ultrasonic wavetransmitting elements and the combination of the ultrasonic wavereceiving elements is described below with reference to FIG. 13.

FIG. 13 shows the case in which a rectangular array sensor is used. Inthe first example, the array sensor is constituted by 64 ultrasonictransducer elements arranged in 8 rows and 8 columns.

The elements shown by horizontal hatching lines are selected astransmitting elements 101T, while the elements shown by oblique hatchinglines are selected as receiving elements 101R.

In FIG. 13, a broken line Als1 denotes a line symmetric axis. The linesymmetric axis Als1 indicates a direction specified by the azimuth angleφ shown in FIG. 9. The transmitting elements 101T are selected andarranged in line symmetry with respect to the line symmetric axis Als1.In addition, adjacent elements are selected as the transmitting elements101T from the plurality of elements.

A broken line Als2 denotes a line symmetric axis that is perpendicularto the line symmetric axis Als1 and passes through a rotationallysymmetric axis Ars. The line symmetric axis Als2 indicates a directionspecified by an angle obtained by adding 180 degrees to the azimuthangle φ shown in FIG. 9. The receiving elements 101R are selected andarranged in line symmetry with respect to the line symmetric axis Als2.In addition, adjacent elements are selected as the receiving elements101R from the plurality of elements. Elements denoted by white squaresare not used for both transmission and reception.

In this case, the receiving elements 101R and the transmitting elements101T are selected and arranged in rotational symmetry about therotationally symmetric axis Ars that extends in the directionperpendicular to the surface of the paper of FIG. 13.

Next, the second example of the combination of ultrasonic wavetransmitting elements and the combination of ultrasonic wave receivingelements is described with reference to FIG. 14.

FIG. 14 shows the case in which a rectangular array sensor is used. Inthe second example, the array sensor is constituted by 30 ultrasonictransducer elements arranged in 6 rows and 6 columns.

The elements shown by horizontal hatching lines are selected astransmitting elements 101T, while the elements shown by oblique hatchinglines are selected as receiving elements 101R. Elements denoted by blacksquares are selected as transmitting/receiving elements 101TR that areused to transmit and receive an ultrasonic wave.

In FIG. 14, a broken line Als1 denotes a line symmetric axis. The linesymmetric axis Als1 indicates the direction specified by the azimuthangle φ shown in FIG. 9. The transmitting elements 101T are selected andarranged in line symmetry with respect to the line symmetric axis Als1.In addition, adjacent elements are selected as the transmitting elements101T from the plurality of elements.

A broken line Als2 denotes a line symmetric axis that is perpendicularto the line symmetric axis Als1 and passes through a rotationallysymmetric axis Ars. The line symmetric axis Als2 indicates the directionspecified by the angle obtained by adding 180 degrees to the azimuthangle φ shown in FIG. 9. The receiving elements 101R are selected andarranged in line symmetry with respect to the line symmetric axis Als2.In addition, adjacent elements are selected as the receiving elements101R from the plurality of elements.

The elements shown by the black squares are the transmitting/receivingelements 101TR that are used for transmission and reception. In theexample shown in FIG. 13, the elements arranged on the diagonals are notused for both transmission and reception. On the other hand, in thesecond example, the elements arranged on the diagonals are used for bothtransmission and reception.

In this case, the receiving elements 101R, the transmitting elements101T, and the transmitting/receiving elements 101TR are selected andarranged in rotational symmetry about the rotationally symmetric axisArs that extends in the direction perpendicular to the surface of thepaper of FIG. 14.

Next, the third example of the combination of transmitting elements andthe combination of receiving elements is described with reference toFIG. 15.

FIG. 15 shows the case in which a rectangular array sensor is used. Inthe third example, the array sensor is constituted by 30 ultrasonictransducer elements arranged in 6 rows and 6 columns.

The elements shown by horizontal hatching lines are selected astransmitting elements 101T, while the elements shown by oblique hatchinglines are selected as receiving elements 101R.

In FIG. 15, a broken line Als1 is a diagonal and denotes a linesymmetric axis. The line symmetric axis Als1 indicates the directionspecified by the azimuth angle φ shown in FIG. 9. The transmittingelements 101T are selected and arranged in line symmetry with respect tothe line symmetric axis Als1. In addition, adjacent elements areselected as the transmitting elements 101T from the plurality ofelements.

A broken line Als2 is a diagonal and denotes a line symmetric axis thatis perpendicular to the line symmetric axis Als1 and passes through arotationally symmetric axis Ars. The line symmetric axis Als2 indicatesthe direction specified by the angle obtained by adding 180 degrees tothe azimuth angle φ shown in FIG. 9. The receiving elements 101R areselected and arranged in line symmetry with respect to the linesymmetric axis Als2. In addition, adjacent elements are selected as thereceiving elements 101R from the plurality of elements. Elements denotedby white squares are not used for both transmission and reception.

In this case, the receiving elements 101R and the transmitting elements101T are selected and arranged in rotational symmetry about therotationally symmetric axis Ars that extends in the directionperpendicular to the surface of the paper of FIG. 15.

Next, the fourth example of the combination of ultrasonic wavetransmitting elements and the combination of ultrasonic wave receivingelements is described with reference to FIG. 16.

FIG. 16 shows the case in which an array sensor having ultrasonictransducer elements arranged in a hexagonal shape is used. In the fourthexample, six ultrasonic transducer elements are arranged on one side ofthe outermost circumference, while the number of ultrasonic transducerelements is smaller toward the inner circumference side. The arraysensor shown in FIG. 16 is constituted by 91 ultrasonic transducerelements.

The elements shown by horizontal hatching lines are selected astransmitting elements 101T, while the elements shown by oblique hatchinglines are selected as receiving elements 101R.

In FIG. 16, a broken line Als1 denotes a line symmetric axis. The linesymmetric axis Als1 indicates the direction specified by the azimuthangle φ shown in FIG. 9. The transmitting elements 101T are selected andarranged in line symmetry with respect to the line symmetric axis Als1.In addition, adjacent elements are selected as the transmitting elements101T from the plurality of elements.

A broken line Als2 denotes a line symmetric axis that is perpendicularto the line symmetric axis Als1 and passes through a rotationallysymmetric axis Ars. The line symmetric axis Als2 indicates the directionspecified by the angle obtained by adding 180 degrees to the azimuthangle φ shown in FIG. 9. The receiving elements 101R are selected andarranged in line symmetry with respect to the line symmetric axis Als2.In addition, adjacent elements are selected as the receiving elements101R from the plurality of elements. An element denoted by a whitehexagon is not used for both transmission and reception.

In this case, the receiving elements 101R and the transmitting elements101T are selected and arranged in rotational symmetry about therotationally symmetric axis Ars that extends in the directionperpendicular to the surface of the paper of FIG. 16.

Next, the fifth example of the combination of ultrasonic wavetransmitting elements and the combination of ultrasonic wave receivingelements is described with reference to FIG. 17.

FIG. 17 shows the case in which an array sensor having ultrasonictransducer elements arranged in a circular shape is used. In the fifthexample, the array sensor is constituted by 121 ultrasonic transducerelements while 24 ultrasonic transducer elements are arranged in acircumferential direction of the sensor.

The elements shown by horizontal hatching lines are selected astransmitting elements 101T, while the elements shown by oblique hatchinglines are selected as receiving elements 101R.

In FIG. 17, a broken line Als1 denotes a line symmetric axis. The linesymmetric axis Als1 indicates the direction specified by the azimuthangle φ shown in FIG. 9. The transmitting elements 101T are selected andarranged in line symmetry with respect to the line symmetric axis Als1.In addition, adjacent elements are selected as the transmitting elements101T from the plurality of elements.

A broken line Als2 denotes a line symmetric axis that is perpendicularto the line symmetric axis Als1 and passes through a rotationallysymmetric axis Ars. The line symmetric axis Als2 indicates the directionspecified by the angle obtained by adding 180 degrees to the azimuthangle φ shown in FIG. 9. The receiving elements 101R are selected andarranged in line symmetry with respect to the line symmetric axis Als2.In addition, adjacent elements are selected as the receiving elements101R from the plurality of elements. An element that is denoted by awhite circle and is located at a central portion of the sensor is notused for both transmission and reception.

In this case, the receiving elements 101R and the transmitting elements101T are selected and arranged in rotational symmetry about therotationally symmetric axis Ars that extends in the directionperpendicular to the surface of the paper of FIG. 17.

In the present embodiment, as described above, the array sensor iscapable of transmitting and receiving an ultrasonic wave whilemaintaining a point focusing effect in a certain refraction angle rangeselected from among a range of 0 to 90 degrees with respect to a normalwithout performing mechanical scanning in all directions.

Next, the configuration and operations of an ultrasonic measurementapparatus according to a second embodiment of the present invention aredescribed with reference to FIGS. 18 to 20.

First, the entire configuration of the ultrasonic measurement apparatusaccording to the second embodiment is described with reference to FIG.18.

FIG. 18 is a block diagram showing the entire configuration of theultrasonic measurement apparatus according to the second embodiment ofthe present invention.

When such an array sensor as shown in FIG. 17 is used, the sizes of theelements that constitute the array sensor vary. Thus, the intensities ofultrasonic waves transmitted by the elements vary, and receivingsensitivity of the elements varies. To avoid this, an ultrasonic wave tobe received is weighted by the apparatus (shown in FIG. 18) according tothe present embodiment so that the intensity of the ultrasonic wave tobe transmitted by each element or receiving sensitivity of each elementis calibrated to reduce the variation in the sensitivity.

The ultrasonic measurement apparatus according to the present embodimentmeasures the object 100 and the reflection source 100A located insidethe object or on the surface of the object with an excellent SN ratio,for example. The ultrasonic measurement apparatus according to thepresent embodiment includes a probe 101, a transmitting/receivingsection 102, a controller 103, and a display unit 104.

The transmitting/receiving section 102 includes an amplitude adjustingsection 102D in addition to the configuration shown in FIG. 1. Theamplitude adjusting section 102D finely adjusts the intensity of anultrasonic wave that is to be transmitted by each element thatconstitutes the array sensor. The controller 103 includes a weightingcircuit 103G that weights the receiving sensitivity of each element.

If it is difficult that the amplitude adjusting section 102D adjusts theintensity of an ultrasonic wave (that is to be transmitted by eachelement) for a technical reason and the amplitude adjusting section 102Dcannot be installed in the apparatus, the weighting circuit 103G mayweight only waveform data on received ultrasonic waves.

The weighting circuit 103G adjusts a waveform of a received signalhaving a delay time added thereto in a similar manner to the amplitudeadjusting section 102D. The weighting circuit 103G has weightingconstants W1 to Wn for the respective elements and multiplies signalsoutput from the elements by the respective weighting constants W1 to Wn.

Next, a method for determining the weighting constants W1 to Wn isdescribed with reference to FIGS. 19 and 20.

FIG. 19 is a flowchart showing content of the method for determining theweighting constants for the ultrasonic measurement apparatus accordingto the present embodiment. FIG. 20 is an explanatory diagram showing thecontent of the method for determining the weighting constants for theultrasonic measurement apparatus according to the present embodiment.

In order to determine an N number of the weighting constants W1 to Wnfor the elements (it is assumed that the number of the elements is N),the elements 101A (sensor illustrated in white in FIG. 20) thatconstitute the array sensor 101B each transmit and receive an ultrasonicwave sequentially to and from a flat plate FP that is located in waterand has a surface parallel to the surface of the sensor 101B so thatreflection data that is obtained from waves reflected from the surfaceof the flat plate FP is stored.

A waveform comparing section WC compares values of the reflection datastored for each element. A constant determining section CD determinesthe weighting constants W1 to Wn (for the respective elements) forcalibration so that the heights of the reflected waves received by allthe elements are the same.

The content of a process for determining the weighting constants isdescribed with reference to FIG. 19.

First, the elements 101A that constitute the array sensor 101B eachtransmit and receive an ultrasonic wave in step S301, as described withreference to FIG. 20, and data is stored in step S302.

Then, it is determined that data received by all the elements is storedin step S303. When the storing is not ended, the element is switched instep S304 and the process returns to step S301. Until the storing of thedata received by all the elements is ended, steps 301 and 302 arerepeated.

After the storing is ended, the waveform comparing section WC compareswave heights of the stored data. Then, the constant determining sectionCD outputs weighting values for the respective elements. Then, theprocess is ended.

The weighting circuit 103G (shown in FIG. 18) multiplies the weightingconstants W1 to Wn by the intensities of waveforms 1 to n so as toreduce a variation in the intensities of the ultrasonic wavestransmitted and received by the respective elements.

The weighting constants for all the elements may be determined. When theintensities of ultrasonic waves transmitted by the elements thatconstitute the circular array sensor shown in FIG. 17 and areconcentrically arranged vary and sensitivity of the elements varies,this method is used to perform calibration and effective in order toreduce the variation in the sensitivity in the process for inspecting anobject in all directions.

In the present embodiment, the array sensor is capable of transmittingand receiving an ultrasonic wave while maintaining the point focusingeffect in a certain refraction angle range selected from among a rangeof 0 to 90 degrees with respect to a normal without performingmechanical scanning in all directions.

In addition, it is possible to detect a defect for a short time with anexcellent SN ratio while suppressing a variation (in the circumferentialdirection of the sensor) in sensitivity of the sensor that receivesultrasonic waves from a surface perpendicular to the normal to thefacing surface of the sensor.

Next, the configuration and operations of an ultrasonic measurementapparatus according to a third embodiment of the present invention aredescribed with reference to FIGS. 21 and 22. The entire configuration ofthe ultrasonic measurement apparatus according to the present embodimentis the same as the configuration shown in FIG. 1 or 18. When theelements that are used for transmission and reception are set as shownin FIG. 13, 14, 15 or 16, the ultrasonic measurement apparatus shown inFIG. 1 can be used. When the elements that are used for transmission andreception are set as shown in FIG. 17, the ultrasonic measurementapparatus shown in FIG. 18 can be used.

FIG. 21 is a flowchart of a method for selecting a transmitting elementand a receiving element from among the elements included in theultrasonic measurement apparatus according to the present embodiment.FIG. 22 is a diagram showing the selected transmitting and receivingelements that are included in the ultrasonic measurement apparatusaccording to the present embodiment.

In the present embodiment, ultrasonic transducer elements that are usedfor transmission and reception can be switched.

FIG. 22 is basically the same as FIG. 13. As described with reference toFIG. 13, the transmitting elements 101T are selected and arranged inline symmetry with respect to the line symmetric axis Als1. In addition,adjacent elements are selected as the transmitting elements 101T fromthe plurality of elements. The receiving elements 101R are selected andarranged in line symmetry with respect to the line symmetric axis Als2that is perpendicular to the line symmetric axis Als1 and passes throughthe rotationally symmetric axis Ars. In addition, adjacent elements areselected as the receiving elements 101R from the plurality of elements.

When the transmitting and receiving elements are set, the elementstransmit and receive ultrasonic waves in a single direction (inspectiondirection). Thus, receiving sensitivity of the sensor may be reduceddepending on the shape of a defect or the direction in which the defectextends. In this case, when the inspection direction is changed, thereceiving sensitivity can be improved.

In the present embodiment, ultrasonic transducer elements that are usedfor transmission and reception can be switched in order to change theinspection direction. Specifically, the line symmetric axis Als1 shownin FIG. 22 extends along a line symmetric axis Als1′ by rotating aboutthe rotationally symmetric axis Ars toward a direction indicated by anarrow shown in FIG. 22 by 45 degrees. The line symmetric axis Als2 shownin FIG. 22 extends along a line symmetric axis Als2′ by rotating aboutthe rotationally symmetric axis Ars toward the direction indicated bythe arrow shown in FIG. 22 by 45 degrees. The axes Als1′ and Als2′ arethe same as the line symmetric axes Als1 and Als2 shown in FIG. 15,respectively. Thus, the inspection direction can be changed by selectingtransmitting elements 101T and receiving elements 101R as described withreference to FIG. 15.

After transmitting elements and the receiving elements are set andarranged in line symmetry with respect to the line symmetric axes, andperform an inspection, the line symmetric axes are rotated as describedabove. Then, transmitting elements and receiving elements are set andarranged in line symmetry with respect to the new line symmetric axes,and perform an inspection. Thus, inspections can be performed in aplurality of directions.

When transmitting elements, receiving elements, andtransmitting/receiving elements are arranged as shown in FIG. 14, theline symmetric axes are rotated by 45 degrees and thereby extend alongnew line symmetric axes, and transmitting elements, receiving elementsand transmitting/receiving elements are set and arranged in linesymmetry with respect to the new line symmetric axes. Thus, aninspection can be performed in a different direction.

When the transmitting elements and the receiving elements are arrangedas shown in FIG. 16, the line symmetric axes are rotated by 60 degreesand 120 degrees and thereby extend along new line symmetric axes, andtransmitting elements and receiving elements are set and arranged inline symmetry with respect to the new line symmetric axes. Thus, aninspection can be performed in a different direction. In addition, whenthe transmitting elements and the receiving elements are arranged asshown in FIG. 16, the line symmetric axes are rotated by 30 degrees andthereby extend along new line symmetric axes, and transmitting elementsand receiving elements can be set and arranged in line symmetry withrespect to the new line symmetric axes.

Furthermore, when the transmitting elements and the receiving elementsare arranged as shown in FIG. 17, the line symmetric axes are rotated by15 degrees and 30 degrees and thereby extend along new line symmetricaxes, and transmitting elements and receiving elements are set andarranged in line symmetry with respect to the new line symmetric axes.Thus, an inspection can be performed in a different direction. Inaddition, when the transmitting elements and the receiving elements arearranged as shown in FIG. 17, the line symmetric axes are rotated by 7.5degrees and thereby extend along new line symmetric axes, andtransmitting elements and receiving elements can be set and arranged inline symmetry with respect to the new line symmetric axes.

Next, a method for performing an inspection while switching transmittingand receiving elements is described with reference to FIG. 21.

When the setting is started, the inspector uses the setting input screen104A (shown in FIG. 1) to enter, as initial settings for the arraysensor, necessary information such as information on the ultrasonictransducer elements that constitute the array sensor and the velocity ofan ultrasonic wave in step S101.

Then, the position of the center of the sensor having the N number ofultrasonic transducer elements, which is a reference of the delay timeand image display, is set in step S102. In general, the center(intersection of a central line Cy and a central line Cx) of theultrasonic transducer elements is set as the center C of the sensor.

Next, the control processing computer 103A calculates a pattern of delaytimes for the respective ultrasonic transducer elements that areincluded in the array sensor in step S103.

Meanwhile, the element selecting circuit 103C uses the informationprovided in the initial setting of step S101 to set an ultrasonictransducer element group that is to be used for transmission andreception in step S104.

The transmitting/receiving section 102 transmits and receives anultrasonic wave on the basis of these settings in step S105, and data isstored in step S106.

Next, it is determined whether or not an operation for switching anelement is ended in step S111. When the switching operation is not endedin step S111, the process returns to step S104 and new transmitting andreceiving elements are set. Then, each of the set transmitting andreceiving elements transmits and receives an ultrasonic wave on thebasis of the settings (performed in steps S102 to S104) in step S105,and data is stored in step S106.

In the present embodiment, the array sensor is capable of transmittingand receiving an ultrasonic wave while maintaining the point focusingeffect in a certain refraction angle range selected from among a rangeof 0 to 90 degrees with respect to a normal without performingmechanical scanning in all directions.

In addition, an SN ratio can be improved by reducing noise that iscaused by a bottom surface echo.

Next, the configuration and operations of an ultrasonic measurementapparatus according to a fourth embodiment of the present invention aredescribed with reference to FIG. 23. The entire configuration of theultrasonic measurement apparatus according to the fourth embodiment isthe same as the configuration shown in FIG. 18.

FIG. 23 is a diagram showing transmitting and receiving elementsselected from the elements included in the ultrasonic measurementapparatus according to the fourth embodiment of the present invention.

FIG. 23 shows the case in which an array sensor having ultrasonictransducer elements arranged in a circular shape (in a similar manner tothe array sensor shown in FIG. 17) is used. In this example, the arraysensor is constituted by 121 ultrasonic transducer elements while 24ultrasonic transducer elements are arranged in a circumferentialdirection of the sensor.

The elements shown by horizontal hatching lines are selected astransmitting elements 101T, while the elements shown by oblique hatchinglines are selected as receiving elements 101R.

In FIG. 23, a broken line Als1 denotes a line symmetric axis. The linesymmetric axis Als1 indicates the direction specified by the azimuthangle φ shown in FIG. 9. The transmitting elements 101T are selected andarranged in line symmetry with respect to the line symmetric axis Als1.In addition, adjacent elements are selected as the transmitting elements101T from the plurality of elements.

A broken line Als2 denotes a line symmetric axis that is perpendicularto the line symmetric axis Als1 and passes through a rotationallysymmetric axis Ars. The line symmetric axis Als2 indicates the directionspecified by the angle obtained by adding 180 degrees to the azimuthangle φ shown in FIG. 9. The receiving elements 101R are selected andarranged in line symmetry with respect to the line symmetric axis Als2.In addition, adjacent elements are selected as the receiving elements101R from the plurality of elements.

In the present embodiment, the transmitting elements and the receivingelements are alternately arranged in the circumferential direction ofthe sensor. This feature is different from the arrangement shown in FIG.17.

In this case, the receiving elements 101R and the transmitting elements101T are selected and arranged in rotational symmetry about therotationally symmetric axis Ars that extends in the directionperpendicular to the surface of the paper of FIG. 23.

All broken lines shown in FIG. 23 pass through the rotationallysymmetric axis Ars and denote line symmetric axes. Transmitting elementsand receiving elements can be selected and arranged in line symmetrywith respect to the line symmetric axes. That is, when the segmentedelements are arranged as shown in FIG. 23, the line symmetric axessufficiently exist. Thus, when focal points are set on the linesymmetric axes, it is not necessary to switch elements. Therefore, it ispossible to reduce noise that is caused by a bottom surface echo andimprove an SN ratio.

Next, the configuration and operations of an ultrasonic measurementapparatus according to a fifth embodiment of the present invention aredescribed.

FIG. 24 is a block diagram showing the configuration of the ultrasonicmeasurement apparatus according to the fifth embodiment of the presentinvention.

The ultrasonic measurement apparatus according to the present embodimentmeasures a reflection source 1400A that is located in an inner portionof an object 1400 or on the surface of the object 1400 while obtainingan excellent SN ratio. The object 1400 is a plate material having athickness of 200 mm to 300 mm, for example.

The ultrasonic measurement apparatus according to the present embodimentincludes a probe 1401, a transmitting/receiving section 1402, acontroller 1403 and a display unit 1404. The probe 1401 has an arraysensor 1401B that transmits and receives an ultrasonic wave to and fromthe object 1400. The array sensor 1401B has a plurality of ultrasonictransducer elements 1401A.

The transmitting/receiving section 1402 includes a pulsar 1402A and areceiver 1402Z. The pulsar 1402A provides a delay time to each of theultrasonic transducer elements 1401A. Each ultrasonic transducer element1401A transmits an ultrasonic wave after a time specified by the delaytime. The receiver 1402Z receives the ultrasonic wave and converts thereceived analog ultrasonic wave into a digital signal as a receptionsignal.

The controller 1403 has a control processing computer 1403A, an elementselecting circuit 1403C, a delay time control circuit 1403D and anadding circuit 1403Z. The control processing computer 1403A has astorage device 1403B.

The element selecting circuit 1403C switches between ultrasonictransducer elements 1401A to select a transmitting element (thattransmits an ultrasonic wave) and a receiving element (that receives anultrasonic wave). The delay time control circuit 1403D controls a delaytime for transmission and a delay time for reception. The adding circuit1403Z adds a plurality of signals received from the receiver 14022. Thecontrol processing computer 1403A controls the element selecting circuit1403C, the delay time control circuit 1403D and the adding circuit1403Z. The control processing computer 1403A stores the received signalsin the storage device 1403B and performs processing on the receivedsignals.

The display unit 1404 has a setting input screen 1404A and a displayscreen 1404Z. Various settings can be displayed on and input through thesetting input screen 1404A. The received signals and an image obtainedby a measurement are displayed on the display screen 1404Z.

Next, operations of the sections of the ultrasonic measurement apparatusare described.

The control processing computer 1403A transmits a transmitting/receivingelement switching signal that is used to select an ultrasonic transducerelement to be used to transmit/receive an ultrasonic wave to the elementselecting circuit 1403C, upon storing a reflection signal received froman object to be measured by transmission and reception of an ultrasonicwave. In addition, the control processing computer 1403A provides,through the delay control circuit 1403D, a delay time to each ultrasonictransducer element so that the element transmits an ultrasonic wave thatwill be focused and receives an ultrasonic wave.

A transmission delay circuit 1402B receives the transmitted signal andthe delay time and transmits the signal (transmission signal) to atransmitting element selector 1402C after a time specified by thereceived delay time. The transmitting element selector 1402C receivesthe transmission signal having the delay time added thereto from thetransmission delay circuit 1402B. Then, the transmitting elementselector 1402C selects a transmitting element on the basis of aselection signal that is used to select the transmitting element and istransmitted from the element selecting circuit 1403C, and transmits thetransmission signal to a transmission amplifier 1402E.

The adding circuit 1403Z may select a signal that is to be received andcorresponds to the transmitted ultrasonic wave, in a similar manner toinformation that is provided to the element selecting circuit 1403C.

Next, the configuration of the ultrasonic measurement apparatusaccording to the present embodiment is described with reference to FIGS.25 and 26.

FIG. 25 is a plan view of the configuration of the array sensor includedin the ultrasonic measurement apparatus according to the fifthembodiment of the present invention. FIG. 26 is a schematic diagramshowing the positions of the gravity centers of the elements included inthe array sensor that is used in the ultrasonic measurement apparatusaccording to the fifth embodiment of the present invention.

As shown in FIG. 25, the array sensor 1401B is formed in a circularshape and has a plurality of ultrasonic transducer elements. The arraysensor 1401B has an inner circumferential portion 1401M and an outercircumferential portion 1401N. The arrangement of the ultrasonictransducer elements included in the inner circumferential portion 1401Mis different from that in the outer circumferential portion 1401N.

The ultrasonic transducer elements included in the inner circumferentialportion 1401M are formed in a hexagonal shape and have a flat surface sothat the surface of the array sensor can be filled efficiently with theflat surfaces of the elements. The sizes of the ultrasonic transducerelements included in the inner circumferential portion 1401M are thesame. In addition, the size of the ultrasonic transducer elementincluded in the inner circumferential portion 1401M is configured sothat directivity of ultrasonic waves transmitted from the elementincluded in the inner circumferential portion 1401M is excellent and animage can be obtained with an improved SN ratio by an inspection.

The ultrasonic transducer elements included in the outer circumferentialportion 1401N are concentrically arranged around the center of thesensor and are formed in a fan shape. The size of the ultrasonictransducer element included in the outer circumferential portion 1401Nis increased toward the outer side of the array sensor.

In the present embodiment, the diameter of a sensor aperture that isconsidered to be necessary for inspection is φ; a central region havinga diameter of ½φ is regarded as the inner circumferential portion 1401M;and the other region of the sensor is regarded as the outercircumferential portion 1401N. The diameter of the inner circumferentialportion 1401M is preferably in a range of ¼φ to ¾φ. The reason for thediameter range is described later with reference to FIG. 29.

As described above, the size of the ultrasonic transducer elementincluded in the inner circumferential portion 1401M is configured sothat directivity of ultrasonic wave transmitted from the elementincluded in the inner circumferential portion 1401M is excellent and animage can be obtained with an improved SN ratio by an inspection. Eachsize of the ultrasonic transducer elements included in the outercircumferential portion 1401N is larger than that in the innercircumferential portion 1401M. The size of the ultrasonic transducerelement included in the outer circumferential portion 1401N is increasedtoward the outer side of the array sensor. Therefore, even when thediameter φ of the sensor aperture is increased, the number of theelements that constitute the array sensor 1401B is not increased.

Next, the gravity centers of the elements that constitute the arraysensor 1401A shown in FIG. 25 are described with reference to FIG. 26.Black dots shown in FIG. 26 denote the gravity centers of the elements.

The elements included in the inner circumferential portion 1401M areformed in a hexagonal shape so that sides of adjacent elements are incontact with each other. Distances L1 between adjacent pairs of theultrasonic transducer elements included in the inner circumferentialportion 1401M are the same.

The elements included in the outer circumferential portion 1401N areconcentrically arranged around the center of the sensor and are formedin a fan shape. Thus, a distance L3 which is measured in thecircumferential direction of the sensor, between the gravity centers ofeach adjacent pair of the ultrasonic transducer elements, is larger thana distance L2 which is measured in a radial direction of the sensor,between the gravity centers of each adjacent pairs of the ultrasonictransducer elements. In addition, the distance L2 which is measured inthe radial direction of the sensor, between the gravity centers of eachadjacent pair of the ultrasonic transducer elements, is the same as thedistance L1 between each adjacent pair of the ultrasonic transducerelements included in the inner circumferential portion 1401M.

Next, a relationship between distances between adjacent pairs of theelements and occurrence of noise (grating lobe) is described below.

In general, when an array sensor having elements is used, andL0≦(λ/(1+|sin θ|) is established, where L0 is a distance between gravitycenters of each adjacent pair of the elements and θ is an angle at whichan ultrasonic wave is transmitted and received, noise (grating lobe)does not occur.

A symbol λ indicates the wavelength of the ultrasonic wave transmittedand received. For example, when an ultrasonic wave is transmitted andreceived to and from a region ranging from −90 degrees to +90 degreesand L0≦λ/2, noise (grating lobe) does not occur. When an ultrasonic waveis transmitted and received to and from a region ranging from −30degrees to +30 degrees and L0≦λ/1.5, noise (grating lobe) does notoccur.

The distance L1 between the gravity centers of each adjacent pair of theultrasonic transducer elements included in the inner circumferentialportion 1401M of the array sensor 1401B is equal to or less than thedistance L0 that does not cause noise (grating lobe).

In addition, the distance L2 which are arranged in the radial directionof the array sensor 1401B, between the gravity centers of each adjacentpair of the ultrasonic transducer elements that are included in theouter circumferential portion 1401N of the array sensor 1401B, is equalto or less than the distance L0 that does not cause noise (gratinglobe). On the other hand, the distance L3 which is measured in thecircumferential direction of the array sensor 1401B, between the gravitycenters of each adjacent pair of the ultrasonic transducer elements thatare included in the outer circumferential portion 1401N of the arraysensor 1401B, is larger than the distance L0 that does not cause noise(grating lobe).

In order to improve an SN ratio, the distances between the gravitycenters of adjacent pairs of all the elements need to be equal to orless than the distance L0 that does not cause noise (grating lobe). Inorder to do so, it is necessary that the lengths of the elementsincluded in the outer circumferential portion 1401N be short in thecircumferential direction. In this case, the elements that constitutethe array sensor 1401B are made small. Therefore, when the diameter φ ofthe aperture is increased, the number of the elements that constitutethe array sensor 1401B is increased.

On the other hand, each size of the ultrasonic transducer elementsincluded in the outer circumferential portion 1401N is larger than thatin the inner circumferential portion 1401M. In addition, the size of theultrasonic transducer element included in the outer circumferentialportion 1401N is increased toward the outer side of the array sensor1401B. Thus, even when the diameter φ of the aperture is increased, thenumber of the elements that constitute the array sensor 1401B is notincreased. However, the distance L3 which is measured in thecircumferential direction, between the gravity centers of each adjacentpair of the ultrasonic transducer elements that are included in theouter circumferential portion 1401N, is larger than the distance L0 thatdoes not cause noise (grating lobe). Thus, when the array sensor 1401Bis used without a change, noise (grating lobe) may occur.

In the present embodiment, the array sensor 1401B shown in FIG. 25 isused. In order to prevent noise (grating lobe), an element that is to beused to transmit and receive an ultrasonic wave is selected from amongthe elements that are included in the outer circumferential portion1401N of the array sensor 1401B on the basis of a transmitting andreceiving direction. The distance L1 between the gravity centers of eachadjacent pair of the ultrasonic transducer elements included in theinner circumferential portion 1401B is equal to or less than thedistance L0 that does not cause noise (grating lobe). Thus, all theelements included in the inner circumferential portion 1401M are used totransmit and receive an ultrasonic wave in all directions. In this case,the transmitting and receiving direction does no indicate an actualdirection in which an ultrasonic wave is transmitted and received. Thetransmitting and receiving direction indicates a direction obtained byprojecting the actual transmitting and receiving direction onto the flatsurface of the array sensor 1401B.

The following describes the case in which an ultrasonic wave istransmitted and received in a direction along an arrow TR1 of FIG. 26.In this case, a distance L1A between the gravity centers of eachadjacent pair 1401M-1 and 1401M-2 of the elements included in the innercircumferential portion 1401M, which is measured in the direction shownby the arrow TR1, is equal to or less than the distance L0 (=L1) thatdoes not cause noise (grating lobe). Thus, when the adjacent elements1401M-1 and 1401M-2 are used for transmission and reception, noise(grating lobe) does not occur.

In addition, a distance L2A which is measured in the direction shown bythe arrow TR1, between the gravity centers of each adjacent pair 1401N-1and 1401N-2 of the elements that are included in the outercircumferential portion 1401N, is equal to or less than the distance L0(=L2) that does not cause noise (grating lobe). Thus, when the adjacentelements 1401N-1 and 1401N-2 are used for transmission and reception,noise (grating lobe) does not occur.

However, a distance L3A which is measured in the direction shown by thearrow TR1, between the gravity centers of each adjacent pair 1401N-3 and1401N-4 of the elements that are included in the outer circumferentialportion 1401N and are arranged in the circumferential direction, islarger than the distance L0 (=L2) that does not cause noise (gratinglobe). Thus, when the adjacent elements 1401N-3 and 1401N-4 are used fortransmission and reception, noise (grating lobe) may occur.

When ultrasonic waves are to be transmitted and received in thedirection shown by the arrow TR1, the pair of elements 1401M-1 and1401M2 and the pair of elements 1401N-1 and 1401N-2 are used and thepair of elements 1401N-3 and 1401N-4 is not used to prevent noise(grating lobe).

It is assumed that elements that are adjacent to each other with thedistance L1 and are included in the inner circumferential portion 1401Mtransmit and receive an ultrasonic wave in directions along arrows TR2and TR3 of FIG. 26. In this assumption, distances between the gravitycenters of the adjacent elements, which are measured in the directionshown by any of the arrows TR2 and TR3, are equal to or less than thedistance L0 (=L1) that does not cause noise (grating lobe). Thus, evenwhen the adjacent elements are used for transmission and reception,noise (grating lobe) does not occur.

The distance L1 between the gravity centers of each adjacent pair of theultrasonic transducer elements included in the inner circumferentialportion 1401M is equal to or less than the distance L0 that does notcause noise (grating lobe). Thus, even when all the elements included inthe inner circumferential portion 1401M are used for transmission andreception, noise (grating lobe) does not occur.

It is assumed that elements that are adjacent to each other with thedistance L2 and are included in the outer circumferential portion 1401Ntransmit or receive an ultrasonic wave in a direction along an arrow TR4of FIG. 26. In this assumption, a distance which is measured in thedirection shown by the arrow TR4, between the gravity centers of theadjacent elements, is equal to or less than the distance L0 (=L2) thatdoes not cause noise (grating lobe). Thus, even when the adjacentelements are used for transmission and reception, noise (grating lobe)does not occur.

It is assumed that elements that are adjacent to each other with thedistance L3 and are included in the outer circumferential portion 1401Ntransmit or receive an ultrasonic wave in a direction along an arrow TR5of FIG. 26. In this assumption, a distance which is measured in thedirection shown by the arrow TR5, between the gravity centers of theadjacent elements, is larger than the distance L0 (=L2) that does notcause noise (grating lobe). Thus, when the adjacent elements are usedfor transmission and reception, noise (grating lobe) may occur.Therefore, when ultrasonic waves are to be transmitted and received inthe direction shown by the arrow TR5, the elements that are adjacent toeach other with the distance L3 are not used.

The array sensor 1401B (shown in FIG. 25) according to the presentembodiment is characterized in that the distance between the gravitycenters of each adjacent pair of the elements that are included in theinner circumferential portion 1401M is equal to or less than a specifieddistance that is the distance L0 (that does not cause noise (gratinglobe)). On the other hand, in the outer circumferential portion 1401N,some of the distances between the gravity centers of adjacent pairs ofthe elements are equal to or less than the specified distance, while theothers of the distances between the gravity centers of the adjacentpairs of the elements are separated with each other with the distancelarger than the specified distance.

The elements included in the inner circumferential portion 1401M may beformed in a triangular, quadrangular, or trapezoidal shape, in additionto the hexagonal shape. The trapezoidal shape is formed by dividing thehexagonal shape shown in FIG. 25 into two along the diagonal of thehexagon shown in FIG. 25.

The elements included in the outer circumferential portion 1401N may beformed in a polygonal shape that is formed by radially dividing thesensor into pieces along a line that passes through the center of thesensor, in addition to the shape of the elements that are concentricallyarranged.

Since the array sensor includes the inner and outer circumferentialportions, the sensor aperture is large. Thus, the array sensor iscapable of inspecting a deep portion. In addition, elements that are tobe used for transmission and reception are selected from the elementsincluded in the outer circumferential portion of the array sensor on thebasis of the transmitting and receiving direction. Thus, an SN ratio canbe improved while noise (grating lobe) does not occur.

Next, an inspection method that is performed by the ultrasonicmeasurement apparatus according to the present embodiment is describedwith reference to FIGS. 27 and 28.

FIG. 27 is a diagram showing the inspection method that is performed bythe ultrasonic measurement apparatus according to the presentembodiment. FIG. 28 is a diagram showing the array sensor that is usedin the ultrasonic measurement apparatus according to the presentembodiment.

When an ultrasonic wave is to be transmitted and received by the 2Darray sensor having the structure shown in FIGS. 25 and 26, theultrasonic transducer elements included in the inner circumferentialportion 1401M are arranged so that the distance L1 between the gravitycenters of each adjacent pair of the elements is equal to or less thanthe specified distance. Thus, the inner circumferential portion 1401Mcan be designed so that a noise source is not present. Therefore, allthe elements included in the inner circumferential portion 1401M can beused to transmit and receive an ultrasonic wave.

The gravity centers of each adjacent pair of the ultrasonic transducerelements included in the outer circumferential portion 1401N andarranged in the circumferential direction are separated with each otherwith the distance L3 that is larger than the specified distance. Thus,these ultrasonic transducer elements may become sources of extremelyhigh frequency noise depending on the transmitting and receivingdirection.

In FIG. 27, the ultrasonic array sensor 1401B is placed on a flatsurface that is perpendicular to a depth direction Dep. The ultrasonicarray sensor 1401B transmits an ultrasonic wave and receives a reflectedwave in and from an ultrasonic transmitting and receiving direction TR.A transmitting and receiving direction TR′ is obtained by projecting theultrasonic transmitting and receiving direction TR onto a flat surfaceof the ultrasonic array sensor 1401B.

FIG. 28 shows the flat surface of the ultrasonic array sensor 1401B. Itis assumed that the gravity centers are projected on axes extending in adirection in which an ultrasonic wave is transmitted and received, andthe direction is projected onto the flat surface of the array sensor1401B to form an ultrasonic transmitting and receiving direction TR′. Inthis assumption, elements that are arranged on axes perpendicular to theultrasonic transmitting and receiving direction TR′ and are included inthe outer circumferential portion 1401N are denoted by 1401N-5, 1401N-6,1401N-7 and 1401N-8. A distance which is measured in the ultrasonictransmitting and receiving direction TR′, between the gravity centers ofthe elements 1401N-5 and 1401N-6, is denoted by L3B. A distance which ismeasured in the ultrasonic transmitting and receiving direction TR′,between the gravity centers of the elements 1401N-6 and 1401N-7, isdenoted by L3C. A distance which is measured in the ultrasonictransmitting and receiving direction TR′, between the gravity centers ofthe elements 1401N-7 and 1401N-8, is denoted by L3D. The distances L3B,L3C and L3D are larger than the distance L0 that does not cause noise(grating lobe). When the elements that are adjacent to each other withthe distance L3B, L3C and L3D transmit ultrasonic waves, ahigh-frequency ultrasonic wave that is called a grating lobe may occurand propagate in an unwanted direction.

Elements arranged in the ultrasonic transmitting and receiving directionTR′ are denoted by 1401N-9 and 1401N-10. A distance L2B which ismeasured in the ultrasonic transmitting and receiving direction TR′,between the gravity centers of the elements 1401N-9 and 1401N-10, issmaller than the distance L0 that does not cause noise (grating lobe).Thus, a grating lobe does not occur.

When elements (shown by hatching lines in FIG. 28) whose projectedgravity centers are separated with each other with a distance that isequal to or less than the specified distance are selected, an inspectioncan be performed while an excellent SN ratio is obtained. In otherwords, when all the elements included in the inner circumferentialportion and some of the elements included in the outer circumferentialportion are selected, an inspection can be performed while an excellentSN ratio is obtained.

Next, a method for selecting an element to be used in the ultrasonicmeasurement apparatus according to the present embodiment, from amongthe elements of the sensor is described with reference to FIG. 29.

FIG. 29 is a diagram showing the method for selecting an element to beused in the ultrasonic measurement apparatus according to the presentembodiment, from among the elements of the sensor.

In order to use all the ultrasonic transducer elements included in theinner circumferential portion 1401N and some of the ultrasonictransducer elements included in the outer circumferential portion 1401Mas described with reference to FIG. 28, ultrasonic transducer elementsare selected as shown in FIG. 29.

Specifically, the following elements are used to perform an inspection:elements whose gravity centers are located in a region surrounded by adashed line shown in FIG. 29 and which are arranged in the projectedultrasonic transmitting and receiving direction TR′. In this case, therectangular region surrounded by the dashed line includes the innercircumferential portion of the sensor in general. In other words, thelength of a short side Ls of the rectangular region is equal to thediameter of the inner circumferential portion 1401M of the array sensor1401B. The length of a long side Ll of the rectangular region is equalto or larger than the diameter (measured in the projected transmittingand receiving direction TR′) of the outer circumferential portion 1401Nof the array sensor 1401B.

When the diameter of the inner circumferential portion 1401M is ½φ (φ isthe diameter of the sensor aperture) as described with reference to FIG.25, the ratio of the short side Ls to the long side Ll is ½. When thediameter of the inner circumferential portion 1401M is in a range of ¼φto ¾φ, the ratio of the short side Ls to the long side Ll is in a rangeof ¼ to ¾.

Next, the inspection method that is performed by the ultrasonicmeasurement apparatus according to the present embodiment is describedwith reference to FIG. 30.

FIG. 30 is a flowchart showing the content of the inspection method thatis performed by the ultrasonic measurement apparatus according to thepresent embodiment.

When the setting is started, the inspector uses the setting input screen1404A (shown in FIG. 24) to enter, as initial settings for the arraysensor, necessary information such as information on the ultrasonictransducer elements that constitute the array sensor 1401B shown in FIG.25 (sizes, arrangements and positions of the elements) and the velocityof an ultrasonic wave in step S1101.

Next, the position of the center of the sensor having the N number ofultrasonic transducer elements, which is a reference of the delay timeand image display, is set on the setting input screen 1404A in stepS1102. In general, the center (intersection of a central line Cy and acentral line Cx) of the ultrasonic transducer elements is set as thecenter C of the sensor.

Next, the control processing computer 1403A calculates a focal point Fon which an ultrasonic wave transmitted by each ultrasonic transducerelement included in the array sensor is focused, and a delay time fortransmission by each ultrasonic transducer element included in the arraysensor, and sets the focal point F and the delay time in step S1103.

Meanwhile, the element selecting circuit 1103C uses the informationprovided in the initial setting of step S1101 to set an ultrasonictransducer element group that is to be used for transmission andreception while the ultrasonic transducer element group does not includeelements that causes noise in step S1104.

Then, in order to transmit and receive an ultrasonic wave to and fromthe focal point F (i) specified in step S1103, the element selectingcircuit 1103C selects an element group (element pattern) that issuitable for the transmitting/receiving direction.

The element group (element pattern) that is to be used and is includedin the ultrasonic measurement apparatus according to the presentembodiment is described with reference to FIGS. 31 and 32.

FIGS. 31 and 32 are diagrams each showing an element pattern that is tobe used and is included in the ultrasonic measurement apparatusaccording to the present embodiment.

FIG. 31 shows a table of an element pattern that is to be used. Thetable shown in FIG. 31 is pre-stored in the storage device 1403B (shownin FIG. 24). The table includes patterns A, B and C. An element that isto be used is indicated by “1”, while an element that is not to be usedis indicated by “0”.

In the pattern A, elements that are to be used as shown in FIG. 32 areselected. In the pattern B, elements that are to be used as shown inFIG. 32 are selected. When the pattern A is used, sector scanning A isperformed as shown in FIG. 32. When the pattern B is used, sectorscanning B is performed as shown in FIG. 32.

Each of the patterns A, B and C is associated with an ultrasonictransmitting and receiving direction. Thus, when the ultrasonictransmitting and receiving direction is determined, a pattern necessaryfor transmission and reception can be selected.

In order to transmit and receive an ultrasonic wave to and from thefocal point F (i) specified in step S1103, the element selecting circuit1103C selects the element pattern described with reference to FIGS. 31and 32 in step S1105 shown in FIG. 30, and the pulsar 1402A transmits anultrasonic wave in step S1105.

Then, the receiver 1402Z stores data (reflection data) on the focalpoint F (i) in step S1106.

Next, the control processing computer 1403A determines whether or notstoring of data on all regions is ended, in step S1107. When the storingis not ended (or when the answer in step S1107 is NO), the processreturns to S1105 and is performed on the next focal point F (i+1). Then,an ultrasonic wave is transmitted and received again and reflection datais stored. Steps S1105 and S1106 are repeated until reflection data onall the regions to be measured is stored.

When it is determined that the storing of data on all the regions isended (or when the answer in step S1107 is YES), the control processingcomputer 1403A creates a map indicative of pixels and pixel values instep S1108 and causes an image to be displayed, in step S1109. Then, theprocess is ended.

A necessary sector-scanned image can be obtained by selecting one of thepatterns shown in FIG. 31. Thus, many sector-scanned images can bestored by electronically switching between the patterns A and B shown inFIG. 32. In addition, a 3D image can be obtained with a high SN ratioeven from a deep portion.

Next, another configuration of the array sensor that is used in theultrasonic measurement apparatus according to the present embodiment isdescribed with reference to FIG. 33.

FIG. 33 is a plan view of the configuration of the array sensor that isused in the ultrasonic measurement apparatus according to the presentembodiment.

As shown in FIG. 33, the array sensor 1401B′ is formed in a circularshape and has a plurality of ultrasonic transducer elements. The arraysensor 1401B′ has an inner circumferential portion 1401M′ and an outercircumferential portion 1401N′. The arrangement of ultrasonic transducerelements included in the inner circumferential portion 1401M′ isdifferent from the arrangement of ultrasonic transducer elementsincluded in the outer circumferential portion 1401N′.

The ultrasonic transducer elements included in the inner circumferentialportion 1401M′ are arranged as follows. The ultrasonic transducerelement located in the innermost circumference of the portion 1401M′ isnot segmented, the element located in the second circumference (that isadjacent to and located on the outer side of the innermostcircumference) of the portion 1401M′ is segmented into 8 elements, theelement located in the third circumference (that is adjacent to andlocated on the outer side of the second circumference) of the portion1401M′ is segmented into 16 elements, the element located in the fourthcircumference (that is adjacent to and located on the outer side of thethird circumference) of the portion 1401M′ is segmented into 24elements, and the element located in the fifth circumference (that isadjacent to and located on the outer side of the fourth circumference)of the portion 1401M′ is segmented into 32 elements. As described above,the number of the segmented elements is increased toward the outercircumferential side. The sizes of the segmented ultrasonic transducerelements included in the inner circumferential portion 1401M′ are notexactly the same but almost the same. In addition, the ultrasonictransducer elements included in the inner circumferential portion 1401M′are configured so that directivity of ultrasonic waves transmitted fromthe elements included in the inner circumferential portion 1401M′ isexcellent and an image can be obtained with an improved SN ratio by aninspection.

The ultrasonic transducer elements included in the outer circumferentialportion 1401N′ are concentrically arranged around the center of thearray sensor and are formed in a fan shape. The size of the ultrasonictransducer element located in the outer circumferential portion 1401N′is increased toward the outer side of the outer circumferential portion1401N′.

The ultrasonic transducer elements included in the inner circumferentialportion 1401M′ are configured so that directivity of ultrasonic waves isexcellent and an image can be obtained with an improved SN ratio by aninspection. Each size of the ultrasonic transducer elements included inthe outer circumferential portion 1401N′ is larger than that in theinner circumferential portion 1401M′. The size of the ultrasonictransducer element included in the outer circumferential portion 1401N′is increased toward the outer circumferential side. Thus, even when thediameter φ of the sensor aperture is increased, the number of theelements that constitute the array sensor 1401B′ is not increased.

As described above, in order to perform an ultrasonic inspection on adeep portion of a plate material having a large thickness, it isnecessary that a sensor has a large aperture. However, since the numberof elements is restricted, it is difficult that a conventional existing2D array sensor has a large aperture. According to the presentinvention, the ultrasonic array sensor has the inner and outercircumferential portions while the arrangement of the elements includedin the inner circumferential portion is different from that in the outercircumferential portion. Thus, the array sensor is capable of having alarge aperture. In addition, since some of the elements included in theouter circumferential portion are used to transmit and receive anultrasonic wave, the array sensor can suppress occurrence of noise.Furthermore, it is possible to inspect a deep portion of a platematerial having a large thickness by using the sensor having the largeaperture while obtaining a high SN ratio and maintaining the pointfocusing effect.

It is, therefore, possible to inspect a deep portion of a plate materialhaving a large thickness by using a small number of ultrasonictransducer elements while obtaining a high SN ratio and maintaining thepoint focusing effect.

1. An ultrasonic measurement method using a two-dimensional array sensorthat has a plurality of ultrasonic transducer elements two-dimensionallyarranged and using a wave reflected from an inner portion of an objectthat is to be measured, comprising the steps of: selecting a group of aplurality of ultrasonic transducer elements for transmission from amongthe ultrasonic transducer elements that constitute the two-dimensionalarray sensor so that the ultrasonic transducer elements selected fortransmission are arranged in line symmetry with respect to a first linesymmetric axis and setting the group selected for transmission, andselecting a group of a plurality of ultrasonic transducer elements forreception from among the ultrasonic transducer elements that constitutethe two-dimensional array sensor so that the ultrasonic transducerelements selected for reception are arranged in line symmetry withrespect to a second line symmetric axis that is perpendicular to thefirst line symmetric axis and passes through a rotationally symmetricaxis and setting the group selected for reception; transmitting anultrasonic wave in the direction of the first line symmetric axis;receiving an ultrasonic wave from the direction of the second linesymmetric axis to store a signal reflected from the inner portion of theobject; and processing the reflected signal to inspect the object. 2.The ultrasonic measurement method according to claim 1, furthercomprising the steps of: selecting a group of a plurality of ultrasonictransducer elements for transmission from among the ultrasonictransducer elements that constitute the two-dimensional array sensor sothat the ultrasonic transducer elements selected for transmission arearranged in line symmetry with respect to a third line symmetric axisthat is set by rotating the first line symmetric axis by a predeterminedangle with respect to the rotationally symmetric axis, and selecting agroup of a plurality of ultrasonic transducer elements for receptionfrom among the ultrasonic transducer elements that constitute thetwo-dimensional array sensor so that the ultrasonic transducer elementsselected for reception are arranged in line symmetry with respect to afourth line symmetric axis that is perpendicular to the third linesymmetric axis and passes through the rotationally symmetric axis;transmitting an ultrasonic wave in the direction of the third linesymmetric axis; receiving an ultrasonic wave from the direction of thefourth line symmetric axis to store a signal reflected from the innerportion of the object; and processing the reflected signal to inspectthe object.
 3. The ultrasonic measurement method according to claim 1,wherein, the group of the ultrasonic transducer elements selected fortransmission and the group of the ultrasonic transducer elementsselected for reception are arranged so that when the groups are rotatedabout the rotationally symmetric axis by 90 degrees, the groups overlapeach other.
 4. The ultrasonic measurement method according to claim 1,further comprising the steps of: setting a plurality of focal points towhich ultrasonic waves are to be transmitted by the two-dimensionalarray sensor; storing signals reflected from the focal points that arelocated in the inner portion of the object; and processing the storedreflected signals to two-dimensionally or three-dimensionally image theinner portion of the object and display an image of the inner portion ofthe object.
 5. The ultrasonic measurement method according to claim 4,further comprising the step of: projecting three-dimensionally storedmeasurement data onto a flat plane and two-dimensionally displaying thedata on an inspection result display screen.
 6. The ultrasonicmeasurement method according to claim 5, further comprising the step ofdisplaying information on a refraction angle φ, an azimuth angle θ and areflected intensity I.
 7. The ultrasonic measurement method according toclaim 6, further comprising the step of specifying a range of therefraction angle φ to be displayed.
 8. The ultrasonic measurement methodaccording to claim 1, further comprising the steps of: performing eitheran operation for weighting a pulse voltage that is to be applied to eachultrasonic transducer element selected for transmission before thetransmission of the ultrasonic wave or an operation for weighting asignal received when the ultrasonic wave is received; and calibratingreflection data and a reflected intensity.
 9. An ultrasonic measurementapparatus comprising: a two-dimensional array sensor having a pluralityof ultrasonic transducer elements two-dimensionally arranged; atransmitting/receiving section that transmits an ultrasonic wave fromeach ultrasonic transducer element included in the two-dimensional arraysensor to an object to be measured and receives a wave reflected fromthe object; a controller that controls the transmitting/receivingsection to generate three-dimensional or two-dimensional image data; anda display unit that displays the three-dimensional or two-dimensionalimage data generated by the controller, wherein the controller includesan element selecting section that selects a group of a plurality ofultrasonic transducer elements for transmission from among theultrasonic transducer elements that constitute the two-dimensional arraysensor so that the ultrasonic transducer elements selected fortransmission are arranged in line symmetry with respect to a first linesymmetric axis to set the group selected for transmission, and selects agroup of a plurality of ultrasonic transducer elements for receptionfrom among the ultrasonic transducer elements that constitute thetwo-dimensional array sensor so that the ultrasonic transducer elementsselected for reception are arranged in line symmetry with respect to asecond line symmetric axis that is perpendicular to the first linesymmetric axis and passes through a rotationally symmetric axis to setthe group selected for reception, and the transmitting/receiving sectionincludes a transmitting element selector and a receiving elementselector, the transmitting element selector being adapted to select, astransmitting elements, the ultrasonic transducer elements set by theelement selecting section, the receiving element selector being adaptedto select, as receiving elements, the ultrasonic transducer elements setby the element selecting section.
 10. The ultrasonic measurementapparatus according to claim 9, wherein the controller includes eitheran amplitude adjusting section or a weighting section, the amplitudeadjusting section being adapted to weight a pulse voltage that is to beapplied to each ultrasonic transducer element selected for transmissionbefore the transmission of the ultrasonic wave, the weighting sectionbeing adapted to weight a signal received when the ultrasonic wave isreceived.
 11. An ultrasonic measurement apparatus comprising: atwo-dimensional array sensor having a plurality of ultrasonic transducerelements two-dimensionally arranged; a transmitting/receiving sectionthat transmits an ultrasonic wave from the two-dimensional array sensorand receives a wave reflected from an inner portion of an object that isto be measured; and a controller that controls thetransmitting/receiving section to cause the transmitting/receivingsection to transmit the ultrasonic wave and receive the ultrasonic wave;wherein the two-dimensional array sensor has an inner circumferentialportion and an outer circumferential portion, the arrangement of theultrasonic transducer elements included in the inner circumferentialportion being different from the arrangement of the ultrasonictransducer elements included in the outer circumferential portion, adistance between the gravity centers of each adjacent pair of theultrasonic transducer elements included in the inner circumferentialportion is equal to or less than a distance at which noise such as agrating lobe is caused, a distance between the gravity centers of eachadjacent pair of some of the ultrasonic transducer elements included inthe outer circumferential portion is equal to or less than the distanceat which noise such as a grating lobe is caused, and a distance betweenthe gravity centers of each adjacent pair of the other ultrasonictransducer elements included in the outer circumferential portion islarger than the distance at which noise such as a grating lobe iscaused, the controller has an element selecting circuit that selects anelement that is to be used from among the plurality of ultrasonictransducer elements that constitute the two-dimensional array sensor,the element selecting circuit selects all the ultrasonic transducerelements included in the inner circumferential portion and ultrasonictransducer elements included in the outer circumferential portion sothat a distance between the gravity centers of each adjacent pair of theselected transducer elements included in the outer circumferentialportion, wherein the distance is measured in a transmitting andreceiving direction obtained by projecting a direction in which anultrasonic is transmitted and received onto a surface of the arraysensor, is equal to or less than the distance at which noise is notcaused.
 12. The ultrasonic measurement apparatus according to claim 11,wherein the element selecting circuit selects elements whose gravitycenters are located in a rectangular region having a long side thatextends in the projected transmitting and receiving direction and ashort side whose length is equal to the diameter of the innercircumferential portion.
 13. An ultrasonic sensor that transmits anultrasonic wave and has a plurality of two-dimensionally ultrasonictransducer elements arranged, the ultrasonic sensor being used in anultrasonic measurement apparatus that performs a measurement using awave reflected from an inner portion of an object that is to bemeasured, comprising: an inner circumferential portion and an outercircumferential portion in which the arrangement of the ultrasonictransducer elements included in the inner circumferential portion isdifferent from the arrangement of the ultrasonic transducer elementsincluded in the outer circumferential portion, wherein a distancebetween the gravity centers of each adjacent pair of the ultrasonictransducer elements included in the inner circumferential portion isequal to or less than a distance at which noise such as a grating lobeis caused, and a distance between the gravity centers of each adjacentpair of some of the ultrasonic transducer elements included in the outercircumferential portion is equal to or less than the distance at whichnoise such as a grating lobe is caused, and a distance between thegravity centers of each adjacent pair of the other ultrasonic transducerelements included in the outer circumferential portion is larger thanthe distance at which noise such as a grating lobe is caused.
 14. Anultrasonic measurement method using a two-dimensional array sensor thathas a plurality of ultrasonic transducer elements two-dimensionallyarranged to transmit an ultrasonic wave and using a wave reflected froman inner portion of an object that is to be measured, comprising thesteps of: using the two-dimensional array sensor that has an innercircumferential portion and an outer circumferential portion, thearrangement of the ultrasonic transducer elements included in the innercircumferential portion being different from the arrangement of theultrasonic transducer elements included in the outer circumferentialportion, wherein a distance between the gravity centers of each adjacentpair of the ultrasonic transducer elements included in the innercircumferential portion is equal to or less than a distance at whichnoise such as a grating lobe is not caused, a distance between thegravity centers of each adjacent pair of some of the ultrasonictransducer elements included in the outer circumferential portion isequal to or less than the distance at which noise is not caused, and adistance between the gravity centers of each adjacent pair of the otherthe ultrasonic transducer elements included in the outer circumferentialportion is larger than the distance at which noise is not caused; andselecting all the ultrasonic transducer elements included in the innercircumferential portion and ultrasonic transducer elements that areadjacent to each other and included in the outer circumferential portionand whose gravity centers are separated with a distance that is equal toor less than the distance at which noise is not caused for theinspection of the object, the distance between the gravity centers ofeach adjacent pair of the selected elements included in the outercircumferential portion being measured in a direction obtained byprojecting, onto the surface of the array sensor, a direction in whichthe ultrasonic wave is transmitted and received.
 15. The ultrasonicmeasurement method according to claim 15, further comprising the stepsof: setting a plurality of focal points to which ultrasonic waves are tobe transmitted by the two-dimensional array sensor; selecting a range ofelements to be used for transmission and reception of the ultrasonicwaves to the focal points; storing signals reflected from the focalpoints located in the inner portion of the object; and processing thestored reflected signals to two-dimensionally or three-dimensionallyimage the inner portion of the object.